<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2024 Workiva-->
<!--r:c3130a22-634b-4dcc-b370-1eef545ce638,g:77882fd2-ba96-4ba7-8f17-5889e4aa4554-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.myriad.com/role/CondensedConsolidatedStatementsofStockholdersEquityunaudited" xlink:type="simple" xlink:href="mygn-20240630.xsd#CondensedConsolidatedStatementsofStockholdersEquityunaudited"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/CondensedConsolidatedStatementsofStockholdersEquityunaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_4f96ebe2-b1fd-420c-8eb3-b03b54d68b52" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_2ab22d41-ada4-4264-9667-83d84b253d0c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_4f96ebe2-b1fd-420c-8eb3-b03b54d68b52" xlink:to="loc_us-gaap_StatementTable_2ab22d41-ada4-4264-9667-83d84b253d0c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_9b6fbf3f-930d-4b44-81af-03d93bc27c64" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_2ab22d41-ada4-4264-9667-83d84b253d0c" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_9b6fbf3f-930d-4b44-81af-03d93bc27c64" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_9b6fbf3f-930d-4b44-81af-03d93bc27c64_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_9b6fbf3f-930d-4b44-81af-03d93bc27c64" xlink:to="loc_us-gaap_EquityComponentDomain_9b6fbf3f-930d-4b44-81af-03d93bc27c64_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_97b87323-0042-4fbc-8f59-b765df3327da" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_9b6fbf3f-930d-4b44-81af-03d93bc27c64" xlink:to="loc_us-gaap_EquityComponentDomain_97b87323-0042-4fbc-8f59-b765df3327da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_a45f4f04-670f-4c19-a5d7-b1819b53ed28" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_97b87323-0042-4fbc-8f59-b765df3327da" xlink:to="loc_us-gaap_CommonStockMember_a45f4f04-670f-4c19-a5d7-b1819b53ed28" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_4ff503a1-9e41-4a52-943f-9e4408141275" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_97b87323-0042-4fbc-8f59-b765df3327da" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_4ff503a1-9e41-4a52-943f-9e4408141275" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_753c8359-c1cd-4f14-9719-0d92a6255e95" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_97b87323-0042-4fbc-8f59-b765df3327da" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_753c8359-c1cd-4f14-9719-0d92a6255e95" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_ce89e866-824b-4ef2-9771-50fb8eac0812" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_97b87323-0042-4fbc-8f59-b765df3327da" xlink:to="loc_us-gaap_RetainedEarningsMember_ce89e866-824b-4ef2-9771-50fb8eac0812" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0f483df1-f0ad-4a45-8fc8-94c8496fed76" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4f96ebe2-b1fd-420c-8eb3-b03b54d68b52" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0f483df1-f0ad-4a45-8fc8-94c8496fed76" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_48e9c166-b011-40c7-a404-25abb5e3e5ae" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0f483df1-f0ad-4a45-8fc8-94c8496fed76" xlink:to="loc_us-gaap_StockholdersEquity_48e9c166-b011-40c7-a404-25abb5e3e5ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_8322f9ec-25c9-4baf-a06b-0a58cf000b74" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0f483df1-f0ad-4a45-8fc8-94c8496fed76" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_8322f9ec-25c9-4baf-a06b-0a58cf000b74" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_d32eaf4f-c323-4276-aeee-a65054b2409e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0f483df1-f0ad-4a45-8fc8-94c8496fed76" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_d32eaf4f-c323-4276-aeee-a65054b2409e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_ce369310-2e3c-4a3b-bdcd-37bba7c6a968" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0f483df1-f0ad-4a45-8fc8-94c8496fed76" xlink:to="loc_us-gaap_NetIncomeLoss_ce369310-2e3c-4a3b-bdcd-37bba7c6a968" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_e4acc142-b649-4371-90c3-c0b962b870ac" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0f483df1-f0ad-4a45-8fc8-94c8496fed76" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_e4acc142-b649-4371-90c3-c0b962b870ac" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_524cb2e7-2e79-442d-ad4b-38ce856f6faa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/REVENUEScheduleofTotalRevenuebyTypeandbyUSversusRestofWorldDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#REVENUEScheduleofTotalRevenuebyTypeandbyUSversusRestofWorldDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/REVENUEScheduleofTotalRevenuebyTypeandbyUSversusRestofWorldDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_6651bf61-4c91-454d-8cf2-b509094fce63" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_706e275a-7b0d-4a29-8cd3-62e99b4686c2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_6651bf61-4c91-454d-8cf2-b509094fce63" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_706e275a-7b0d-4a29-8cd3-62e99b4686c2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_a1df88e0-81aa-4bee-bad4-0c778ad97304" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_706e275a-7b0d-4a29-8cd3-62e99b4686c2" xlink:to="loc_srt_ProductOrServiceAxis_a1df88e0-81aa-4bee-bad4-0c778ad97304" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_a1df88e0-81aa-4bee-bad4-0c778ad97304_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_a1df88e0-81aa-4bee-bad4-0c778ad97304" xlink:to="loc_srt_ProductsAndServicesDomain_a1df88e0-81aa-4bee-bad4-0c778ad97304_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_5bc8cf61-b535-4d94-bf85-a89dff4157b2" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_a1df88e0-81aa-4bee-bad4-0c778ad97304" xlink:to="loc_srt_ProductsAndServicesDomain_5bc8cf61-b535-4d94-bf85-a89dff4157b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_HereditaryCancerTestingMember_b1f2b584-18d8-4fa3-b43d-d66b79e29c33" xlink:href="mygn-20240630.xsd#mygn_HereditaryCancerTestingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_5bc8cf61-b535-4d94-bf85-a89dff4157b2" xlink:to="loc_mygn_HereditaryCancerTestingMember_b1f2b584-18d8-4fa3-b43d-d66b79e29c33" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_TumorProfilingMember_bfabbd22-e8ec-4ac1-9750-71f86d61dab3" xlink:href="mygn-20240630.xsd#mygn_TumorProfilingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_5bc8cf61-b535-4d94-bf85-a89dff4157b2" xlink:to="loc_mygn_TumorProfilingMember_bfabbd22-e8ec-4ac1-9750-71f86d61dab3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_PrenatalTestingMember_7a7750ea-f1c1-445a-975e-5d53b245efa3" xlink:href="mygn-20240630.xsd#mygn_PrenatalTestingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_5bc8cf61-b535-4d94-bf85-a89dff4157b2" xlink:to="loc_mygn_PrenatalTestingMember_7a7750ea-f1c1-445a-975e-5d53b245efa3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_PharmacogenomicsMember_4304b349-7e35-4dfb-b830-b21bcc7dccd6" xlink:href="mygn-20240630.xsd#mygn_PharmacogenomicsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_5bc8cf61-b535-4d94-bf85-a89dff4157b2" xlink:to="loc_mygn_PharmacogenomicsMember_4304b349-7e35-4dfb-b830-b21bcc7dccd6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_064ef3bb-69ee-46ea-8082-c96e99a7bb67" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_706e275a-7b0d-4a29-8cd3-62e99b4686c2" xlink:to="loc_srt_StatementGeographicalAxis_064ef3bb-69ee-46ea-8082-c96e99a7bb67" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_064ef3bb-69ee-46ea-8082-c96e99a7bb67_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_064ef3bb-69ee-46ea-8082-c96e99a7bb67" xlink:to="loc_srt_SegmentGeographicalDomain_064ef3bb-69ee-46ea-8082-c96e99a7bb67_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_20aad283-6871-4bfa-a122-3991de36660d" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_064ef3bb-69ee-46ea-8082-c96e99a7bb67" xlink:to="loc_srt_SegmentGeographicalDomain_20aad283-6871-4bfa-a122-3991de36660d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_4ee6c34a-c8bc-45be-a349-06aeb56d0611" xlink:href="https://xbrl.sec.gov/country/2024/country-2024.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_20aad283-6871-4bfa-a122-3991de36660d" xlink:to="loc_country_US_4ee6c34a-c8bc-45be-a349-06aeb56d0611" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_907a15cb-54d4-4354-b6e9-88447a431814" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_20aad283-6871-4bfa-a122-3991de36660d" xlink:to="loc_us-gaap_NonUsMember_907a15cb-54d4-4354-b6e9-88447a431814" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_95a4778b-0497-4c47-be21-968e406355ac" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_6651bf61-4c91-454d-8cf2-b509094fce63" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_95a4778b-0497-4c47-be21-968e406355ac" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/REVENUENarrativeDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#REVENUENarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/REVENUENarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_301f558e-0f52-45ef-8e81-39508d3e3460" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTable_4e0896e0-3171-4138-9234-a3117c055f2a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_301f558e-0f52-45ef-8e81-39508d3e3460" xlink:to="loc_us-gaap_ConcentrationRiskTable_4e0896e0-3171-4138-9234-a3117c055f2a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_c1a3f769-29fd-4836-9e3a-ad93ab18b559" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_4e0896e0-3171-4138-9234-a3117c055f2a" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_c1a3f769-29fd-4836-9e3a-ad93ab18b559" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_c1a3f769-29fd-4836-9e3a-ad93ab18b559_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_c1a3f769-29fd-4836-9e3a-ad93ab18b559" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_c1a3f769-29fd-4836-9e3a-ad93ab18b559_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_b71aa947-7e8e-49b8-9ecd-636b73ae502e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_c1a3f769-29fd-4836-9e3a-ad93ab18b559" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_b71aa947-7e8e-49b8-9ecd-636b73ae502e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GovernmentContractsConcentrationRiskMember_3c3e4797-5db8-465a-95cd-dcac75907876" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GovernmentContractsConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_b71aa947-7e8e-49b8-9ecd-636b73ae502e" xlink:to="loc_us-gaap_GovernmentContractsConcentrationRiskMember_3c3e4797-5db8-465a-95cd-dcac75907876" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_a2f7768c-2178-4bc0-a440-a29e868498b1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_b71aa947-7e8e-49b8-9ecd-636b73ae502e" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_a2f7768c-2178-4bc0-a440-a29e868498b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_871be379-4421-42df-b440-25e6c76e83a2" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_4e0896e0-3171-4138-9234-a3117c055f2a" xlink:to="loc_srt_MajorCustomersAxis_871be379-4421-42df-b440-25e6c76e83a2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_871be379-4421-42df-b440-25e6c76e83a2_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_871be379-4421-42df-b440-25e6c76e83a2" xlink:to="loc_srt_NameOfMajorCustomerDomain_871be379-4421-42df-b440-25e6c76e83a2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_5ef626c1-1fd2-44ed-a6eb-ecee242165ba" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_871be379-4421-42df-b440-25e6c76e83a2" xlink:to="loc_srt_NameOfMajorCustomerDomain_5ef626c1-1fd2-44ed-a6eb-ecee242165ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_MedicareMember_e17bc547-69ef-4f7c-9359-e050fff119d3" xlink:href="mygn-20240630.xsd#mygn_MedicareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_5ef626c1-1fd2-44ed-a6eb-ecee242165ba" xlink:to="loc_mygn_MedicareMember_e17bc547-69ef-4f7c-9359-e050fff119d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_592378c1-67eb-42b5-8984-c8db873660b0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_4e0896e0-3171-4138-9234-a3117c055f2a" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_592378c1-67eb-42b5-8984-c8db873660b0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_592378c1-67eb-42b5-8984-c8db873660b0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_592378c1-67eb-42b5-8984-c8db873660b0" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_592378c1-67eb-42b5-8984-c8db873660b0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_5a683d61-dfa1-4194-8640-7a165160f0f9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_592378c1-67eb-42b5-8984-c8db873660b0" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_5a683d61-dfa1-4194-8640-7a165160f0f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerMember_849c0054-9ebd-4a62-8cc1-5ab697d5d5ce" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueFromContractWithCustomerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_5a683d61-dfa1-4194-8640-7a165160f0f9" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerMember_849c0054-9ebd-4a62-8cc1-5ab697d5d5ce" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableMember_5cf1e08f-7ee5-49a0-ad78-7a32af22d19c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_5a683d61-dfa1-4194-8640-7a165160f0f9" xlink:to="loc_us-gaap_AccountsReceivableMember_5cf1e08f-7ee5-49a0-ad78-7a32af22d19c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetCumulativeCatchUpAdjustmentToRevenueChangeInEstimateOfTransactionPrice_26fd7eef-a1f2-48bb-b5c0-b74dfb0d075e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContractWithCustomerAssetCumulativeCatchUpAdjustmentToRevenueChangeInEstimateOfTransactionPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_301f558e-0f52-45ef-8e81-39508d3e3460" xlink:to="loc_us-gaap_ContractWithCustomerAssetCumulativeCatchUpAdjustmentToRevenueChangeInEstimateOfTransactionPrice_26fd7eef-a1f2-48bb-b5c0-b74dfb0d075e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_IncreaseDecreaseInEarningsLossPerShare_ef5d841c-bec2-4935-9327-a6982d217c2e" xlink:href="mygn-20240630.xsd#mygn_IncreaseDecreaseInEarningsLossPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_301f558e-0f52-45ef-8e81-39508d3e3460" xlink:to="loc_mygn_IncreaseDecreaseInEarningsLossPerShare_ef5d841c-bec2-4935-9327-a6982d217c2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetCumulativeCatchUpAdjustmentToRevenueModificationOfContract_01db3f14-6bf9-4c57-a2d8-02486ae4bb81" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContractWithCustomerAssetCumulativeCatchUpAdjustmentToRevenueModificationOfContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_301f558e-0f52-45ef-8e81-39508d3e3460" xlink:to="loc_us-gaap_ContractWithCustomerAssetCumulativeCatchUpAdjustmentToRevenueModificationOfContract_01db3f14-6bf9-4c57-a2d8-02486ae4bb81" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostGross_f52030ee-dcaa-468c-8934-895285e7cb54" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CapitalizedContractCostGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_301f558e-0f52-45ef-8e81-39508d3e3460" xlink:to="loc_us-gaap_CapitalizedContractCostGross_f52030ee-dcaa-468c-8934-895285e7cb54" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_019e66b5-01c4-402f-9a77-6b47b87b6661" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_301f558e-0f52-45ef-8e81-39508d3e3460" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_019e66b5-01c4-402f-9a77-6b47b87b6661" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/MARKETABLEINVESTMENTSECURITIESScheduleofFairValueforAvailableforSaleSecuritiesbyMajorSecurityTypeandClassofSecurityDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#MARKETABLEINVESTMENTSECURITIESScheduleofFairValueforAvailableforSaleSecuritiesbyMajorSecurityTypeandClassofSecurityDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/MARKETABLEINVESTMENTSECURITIESScheduleofFairValueforAvailableforSaleSecuritiesbyMajorSecurityTypeandClassofSecurityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_e1f60d2f-2664-488c-8671-86604f9deadc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_1f77e552-f9c5-4462-868a-87558f427edc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_e1f60d2f-2664-488c-8671-86604f9deadc" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_1f77e552-f9c5-4462-868a-87558f427edc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_f74526f2-1dfd-46eb-8d35-456c85664d57" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_1f77e552-f9c5-4462-868a-87558f427edc" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_f74526f2-1dfd-46eb-8d35-456c85664d57" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_f74526f2-1dfd-46eb-8d35-456c85664d57_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_f74526f2-1dfd-46eb-8d35-456c85664d57" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_f74526f2-1dfd-46eb-8d35-456c85664d57_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_98f04833-4bb2-41bc-9ef8-193db39c6fc6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_f74526f2-1dfd-46eb-8d35-456c85664d57" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_98f04833-4bb2-41bc-9ef8-193db39c6fc6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashMember_9758745e-1337-457f-b8ef-b99e227c6d57" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_98f04833-4bb2-41bc-9ef8-193db39c6fc6" xlink:to="loc_us-gaap_CashMember_9758745e-1337-457f-b8ef-b99e227c6d57" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashEquivalentsMember_cc4ca6b3-eeeb-46c6-85d7-e92e5a61c04b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_98f04833-4bb2-41bc-9ef8-193db39c6fc6" xlink:to="loc_us-gaap_CashEquivalentsMember_cc4ca6b3-eeeb-46c6-85d7-e92e5a61c04b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_76f4ff67-8bf6-4eb0-b118-cc788b847594" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_1f77e552-f9c5-4462-868a-87558f427edc" xlink:to="loc_us-gaap_FinancialInstrumentAxis_76f4ff67-8bf6-4eb0-b118-cc788b847594" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_76f4ff67-8bf6-4eb0-b118-cc788b847594_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_76f4ff67-8bf6-4eb0-b118-cc788b847594" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_76f4ff67-8bf6-4eb0-b118-cc788b847594_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_dcd8a624-37ad-47ff-b8bc-eef8dea03946" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_76f4ff67-8bf6-4eb0-b118-cc788b847594" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_dcd8a624-37ad-47ff-b8bc-eef8dea03946" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_f01d18fa-d8f5-4b29-9457-f919544a66fe" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_dcd8a624-37ad-47ff-b8bc-eef8dea03946" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_f01d18fa-d8f5-4b29-9457-f919544a66fe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MunicipalBondsMember_b3fd799e-09d8-484e-b6c3-3264e49dae3a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_MunicipalBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_dcd8a624-37ad-47ff-b8bc-eef8dea03946" xlink:to="loc_us-gaap_MunicipalBondsMember_b3fd799e-09d8-484e-b6c3-3264e49dae3a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_8e72d283-9c37-42fd-9cf4-ddfc04d7267e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_e1f60d2f-2664-488c-8671-86604f9deadc" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_8e72d283-9c37-42fd-9cf4-ddfc04d7267e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_CashAndCashEquivalentsCarryingValueBeforeReclassificationOfAssetsHeldForSale_28a6c4ee-fb59-4e91-9ce6-6e5da1623c27" xlink:href="mygn-20240630.xsd#mygn_CashAndCashEquivalentsCarryingValueBeforeReclassificationOfAssetsHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_8e72d283-9c37-42fd-9cf4-ddfc04d7267e" xlink:to="loc_mygn_CashAndCashEquivalentsCarryingValueBeforeReclassificationOfAssetsHeldForSale_28a6c4ee-fb59-4e91-9ce6-6e5da1623c27" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_CashAndCashEquivalentsFairValueDisclosureBeforeReclassificationOfAssetsHeldForSale_32bd312f-74b5-44f8-a920-db476cc808b4" xlink:href="mygn-20240630.xsd#mygn_CashAndCashEquivalentsFairValueDisclosureBeforeReclassificationOfAssetsHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_8e72d283-9c37-42fd-9cf4-ddfc04d7267e" xlink:to="loc_mygn_CashAndCashEquivalentsFairValueDisclosureBeforeReclassificationOfAssetsHeldForSale_32bd312f-74b5-44f8-a920-db476cc808b4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_CashAndCashEquivalentsAmortizedCostReclassificationToAssetsHeldForSale_615ba367-05fe-4843-80d0-27588cb1d689" xlink:href="mygn-20240630.xsd#mygn_CashAndCashEquivalentsAmortizedCostReclassificationToAssetsHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_8e72d283-9c37-42fd-9cf4-ddfc04d7267e" xlink:to="loc_mygn_CashAndCashEquivalentsAmortizedCostReclassificationToAssetsHeldForSale_615ba367-05fe-4843-80d0-27588cb1d689" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_CashAndCashEquivalentsReclassificationToAssetsHeldForSale_427014bd-14d5-4861-9f23-f34c7961e61a" xlink:href="mygn-20240630.xsd#mygn_CashAndCashEquivalentsReclassificationToAssetsHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_8e72d283-9c37-42fd-9cf4-ddfc04d7267e" xlink:to="loc_mygn_CashAndCashEquivalentsReclassificationToAssetsHeldForSale_427014bd-14d5-4861-9f23-f34c7961e61a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_cd4380d1-5bcd-49f9-a845-193d8c9499a0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_8e72d283-9c37-42fd-9cf4-ddfc04d7267e" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_cd4380d1-5bcd-49f9-a845-193d8c9499a0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_6f89eb90-614c-48c8-8d2d-506115da2cab" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_8e72d283-9c37-42fd-9cf4-ddfc04d7267e" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_6f89eb90-614c-48c8-8d2d-506115da2cab" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAbstract_ad85435c-74ad-46f6-92dc-523ecc5291a0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_e1f60d2f-2664-488c-8671-86604f9deadc" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAbstract_ad85435c-74ad-46f6-92dc-523ecc5291a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_5717ae73-9678-4a46-80e5-7e311cd07912" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_ad85435c-74ad-46f6-92dc-523ecc5291a0" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_5717ae73-9678-4a46-80e5-7e311cd07912" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_71db7549-ba04-4ef9-8ef3-d4b15901d512" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_ad85435c-74ad-46f6-92dc-523ecc5291a0" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_71db7549-ba04-4ef9-8ef3-d4b15901d512" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_a752ea93-4f7d-4fcc-bf5b-876ede1fee53" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_ad85435c-74ad-46f6-92dc-523ecc5291a0" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_a752ea93-4f7d-4fcc-bf5b-876ede1fee53" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_0ac21f57-cffd-4a65-924f-8a11a56ada52" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_ad85435c-74ad-46f6-92dc-523ecc5291a0" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_0ac21f57-cffd-4a65-924f-8a11a56ada52" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsAndCashAbstract_5d7df935-ca21-4dc6-8e29-db88cbd49749" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentsAndCashAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_e1f60d2f-2664-488c-8671-86604f9deadc" xlink:to="loc_us-gaap_InvestmentsAndCashAbstract_5d7df935-ca21-4dc6-8e29-db88cbd49749" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_InvestmentsAndCashAmortizedCost_9d6f887e-6926-4620-af4b-cd3072ac6e16" xlink:href="mygn-20240630.xsd#mygn_InvestmentsAndCashAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentsAndCashAbstract_5d7df935-ca21-4dc6-8e29-db88cbd49749" xlink:to="loc_mygn_InvestmentsAndCashAmortizedCost_9d6f887e-6926-4620-af4b-cd3072ac6e16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_InvestmentsAndCashAccumulatedGrossUnrealizedGainBeforeTax_694244b9-c479-48ae-9662-8f36161247b5" xlink:href="mygn-20240630.xsd#mygn_InvestmentsAndCashAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentsAndCashAbstract_5d7df935-ca21-4dc6-8e29-db88cbd49749" xlink:to="loc_mygn_InvestmentsAndCashAccumulatedGrossUnrealizedGainBeforeTax_694244b9-c479-48ae-9662-8f36161247b5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_InvestmentsAndCashAccumulatedGrossUnrealizedLossBeforeTax_ca258625-ac8e-4dbc-8d9e-b6858ff98e6a" xlink:href="mygn-20240630.xsd#mygn_InvestmentsAndCashAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentsAndCashAbstract_5d7df935-ca21-4dc6-8e29-db88cbd49749" xlink:to="loc_mygn_InvestmentsAndCashAccumulatedGrossUnrealizedLossBeforeTax_ca258625-ac8e-4dbc-8d9e-b6858ff98e6a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsAndCash_5f78e3d4-08cd-48a5-be43-61398d35370d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentsAndCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentsAndCashAbstract_5d7df935-ca21-4dc6-8e29-db88cbd49749" xlink:to="loc_us-gaap_InvestmentsAndCash_5f78e3d4-08cd-48a5-be43-61398d35370d" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/MARKETABLEINVESTMENTSECURITIESScheduleofCashCashEquivalentsandMaturitiesofDebtSecuritiesClassifiedasAvailableForSaleSecuritiesDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#MARKETABLEINVESTMENTSECURITIESScheduleofCashCashEquivalentsandMaturitiesofDebtSecuritiesClassifiedasAvailableForSaleSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/MARKETABLEINVESTMENTSECURITIESScheduleofCashCashEquivalentsandMaturitiesofDebtSecuritiesClassifiedasAvailableForSaleSecuritiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_33fa0a50-ed95-4bc4-97de-9b9598ade2ed" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_b4d03a3f-ac60-4993-b8ec-c2a7d56c0a0a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_33fa0a50-ed95-4bc4-97de-9b9598ade2ed" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_b4d03a3f-ac60-4993-b8ec-c2a7d56c0a0a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_d0d91859-d854-4b19-8108-29b3f4f86502" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_b4d03a3f-ac60-4993-b8ec-c2a7d56c0a0a" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_d0d91859-d854-4b19-8108-29b3f4f86502" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_d0d91859-d854-4b19-8108-29b3f4f86502_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_d0d91859-d854-4b19-8108-29b3f4f86502" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_d0d91859-d854-4b19-8108-29b3f4f86502_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_2bc78efa-15bd-4707-909e-8be1cc12f913" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_d0d91859-d854-4b19-8108-29b3f4f86502" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_2bc78efa-15bd-4707-909e-8be1cc12f913" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashMember_b628fbd6-9dde-44fb-8542-6522eeb6482d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_2bc78efa-15bd-4707-909e-8be1cc12f913" xlink:to="loc_us-gaap_CashMember_b628fbd6-9dde-44fb-8542-6522eeb6482d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashEquivalentsMember_86deacf1-d7b8-45f1-b922-36e74349a4cb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_2bc78efa-15bd-4707-909e-8be1cc12f913" xlink:to="loc_us-gaap_CashEquivalentsMember_86deacf1-d7b8-45f1-b922-36e74349a4cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisRollingMaturityAbstract_1542d4e7-733a-4b2e-a1e7-05d826421d44" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisRollingMaturityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_33fa0a50-ed95-4bc4-97de-9b9598ade2ed" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisRollingMaturityAbstract_1542d4e7-733a-4b2e-a1e7-05d826421d44" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_CashAndCashEquivalentsCarryingValueBeforeReclassificationOfAssetsHeldForSale_c5acc179-bfda-412d-8dca-88627bb40c39" xlink:href="mygn-20240630.xsd#mygn_CashAndCashEquivalentsCarryingValueBeforeReclassificationOfAssetsHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisRollingMaturityAbstract_1542d4e7-733a-4b2e-a1e7-05d826421d44" xlink:to="loc_mygn_CashAndCashEquivalentsCarryingValueBeforeReclassificationOfAssetsHeldForSale_c5acc179-bfda-412d-8dca-88627bb40c39" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableforsaleAmortizedCostAbstract_f04e6d96-4c60-4381-8e9a-501799dbfd7e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtSecuritiesAvailableforsaleAmortizedCostAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisRollingMaturityAbstract_1542d4e7-733a-4b2e-a1e7-05d826421d44" xlink:to="loc_us-gaap_DebtSecuritiesAvailableforsaleAmortizedCostAbstract_f04e6d96-4c60-4381-8e9a-501799dbfd7e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost_748ddc74-c572-4c30-b645-f06c76226a27" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesAvailableforsaleAmortizedCostAbstract_f04e6d96-4c60-4381-8e9a-501799dbfd7e" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost_748ddc74-c572-4c30-b645-f06c76226a27" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_InvestmentsAndCashAmortizedCostBeforeReclassificationOfAssetsHeldForSale_812e2223-6244-490a-b500-048a870f3608" xlink:href="mygn-20240630.xsd#mygn_InvestmentsAndCashAmortizedCostBeforeReclassificationOfAssetsHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisRollingMaturityAbstract_1542d4e7-733a-4b2e-a1e7-05d826421d44" xlink:to="loc_mygn_InvestmentsAndCashAmortizedCostBeforeReclassificationOfAssetsHeldForSale_812e2223-6244-490a-b500-048a870f3608" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_CashAndCashEquivalentsAmortizedCostReclassificationToAssetsHeldForSale_28022c90-f171-467f-a937-354ab62e11e9" xlink:href="mygn-20240630.xsd#mygn_CashAndCashEquivalentsAmortizedCostReclassificationToAssetsHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisRollingMaturityAbstract_1542d4e7-733a-4b2e-a1e7-05d826421d44" xlink:to="loc_mygn_CashAndCashEquivalentsAmortizedCostReclassificationToAssetsHeldForSale_28022c90-f171-467f-a937-354ab62e11e9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_InvestmentsAndCashAmortizedCost_69f66d5b-c189-40af-b237-6d7365021d54" xlink:href="mygn-20240630.xsd#mygn_InvestmentsAndCashAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisRollingMaturityAbstract_1542d4e7-733a-4b2e-a1e7-05d826421d44" xlink:to="loc_mygn_InvestmentsAndCashAmortizedCost_69f66d5b-c189-40af-b237-6d7365021d54" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_f921731b-1c50-418c-8f46-9613eadb9f8d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_33fa0a50-ed95-4bc4-97de-9b9598ade2ed" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_f921731b-1c50-418c-8f46-9613eadb9f8d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_CashAndCashEquivalentsFairValueDisclosureBeforeReclassificationOfAssetsHeldForSale_d0e943d4-f7a6-4024-aa10-8f5a65314308" xlink:href="mygn-20240630.xsd#mygn_CashAndCashEquivalentsFairValueDisclosureBeforeReclassificationOfAssetsHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_f921731b-1c50-418c-8f46-9613eadb9f8d" xlink:to="loc_mygn_CashAndCashEquivalentsFairValueDisclosureBeforeReclassificationOfAssetsHeldForSale_d0e943d4-f7a6-4024-aa10-8f5a65314308" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAbstract_2e8cbffe-f415-4301-b7e9-26feff232ef6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_f921731b-1c50-418c-8f46-9613eadb9f8d" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAbstract_2e8cbffe-f415-4301-b7e9-26feff232ef6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_39f9bdda-48d7-4183-bc42-5207feb10321" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_2e8cbffe-f415-4301-b7e9-26feff232ef6" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_39f9bdda-48d7-4183-bc42-5207feb10321" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_InvestmentsAndCashBeforeReclassificationOfAssetsHeldForSale_e95a1b44-5aed-4a4a-8b16-be15caddc773" xlink:href="mygn-20240630.xsd#mygn_InvestmentsAndCashBeforeReclassificationOfAssetsHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_f921731b-1c50-418c-8f46-9613eadb9f8d" xlink:to="loc_mygn_InvestmentsAndCashBeforeReclassificationOfAssetsHeldForSale_e95a1b44-5aed-4a4a-8b16-be15caddc773" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_CashAndCashEquivalentsReclassificationToAssetsHeldForSale_acaf1a7a-7753-45c5-97d8-6d0aeea5626e" xlink:href="mygn-20240630.xsd#mygn_CashAndCashEquivalentsReclassificationToAssetsHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_f921731b-1c50-418c-8f46-9613eadb9f8d" xlink:to="loc_mygn_CashAndCashEquivalentsReclassificationToAssetsHeldForSale_acaf1a7a-7753-45c5-97d8-6d0aeea5626e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsAndCash_4949a893-7ac6-4673-ae45-b4788d4ade3b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentsAndCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueRollingMaturityAbstract_f921731b-1c50-418c-8f46-9613eadb9f8d" xlink:to="loc_us-gaap_InvestmentsAndCash_4949a893-7ac6-4673-ae45-b4788d4ade3b" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/FAIRVALUEMEASUREMENTSNarrativeDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#FAIRVALUEMEASUREMENTSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/FAIRVALUEMEASUREMENTSNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_2a968fc7-0506-46d6-b97f-3f2b82c34a52" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_583edc3c-3835-4e90-a595-0f96ae5de906" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_2a968fc7-0506-46d6-b97f-3f2b82c34a52" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_583edc3c-3835-4e90-a595-0f96ae5de906" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_15fd9180-f557-4059-88f6-b69848913321" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_583edc3c-3835-4e90-a595-0f96ae5de906" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_15fd9180-f557-4059-88f6-b69848913321" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_15fd9180-f557-4059-88f6-b69848913321_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_15fd9180-f557-4059-88f6-b69848913321" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_15fd9180-f557-4059-88f6-b69848913321_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_5e135101-b89d-41f9-bd57-389e7404bb5c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_15fd9180-f557-4059-88f6-b69848913321" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_5e135101-b89d-41f9-bd57-389e7404bb5c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_cd142431-61e6-4420-a077-b0dc4b2340d0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_5e135101-b89d-41f9-bd57-389e7404bb5c" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_cd142431-61e6-4420-a077-b0dc4b2340d0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_c83a48a2-c605-492a-93ec-2e71f6067cae" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_583edc3c-3835-4e90-a595-0f96ae5de906" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_c83a48a2-c605-492a-93ec-2e71f6067cae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c83a48a2-c605-492a-93ec-2e71f6067cae_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_c83a48a2-c605-492a-93ec-2e71f6067cae" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c83a48a2-c605-492a-93ec-2e71f6067cae_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6f220b27-8a28-4917-a208-0a7cd8d1d281" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_c83a48a2-c605-492a-93ec-2e71f6067cae" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6f220b27-8a28-4917-a208-0a7cd8d1d281" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_GatewayGenomicsLLCMember_82243c44-20e5-4c79-8b65-36fca835a4e9" xlink:href="mygn-20240630.xsd#mygn_GatewayGenomicsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6f220b27-8a28-4917-a208-0a7cd8d1d281" xlink:to="loc_mygn_GatewayGenomicsLLCMember_82243c44-20e5-4c79-8b65-36fca835a4e9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_dcc022e8-8264-4291-98ba-b98ddc4338ce" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_583edc3c-3835-4e90-a595-0f96ae5de906" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_dcc022e8-8264-4291-98ba-b98ddc4338ce" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_dcc022e8-8264-4291-98ba-b98ddc4338ce_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_dcc022e8-8264-4291-98ba-b98ddc4338ce" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_dcc022e8-8264-4291-98ba-b98ddc4338ce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_9fad4b4f-fdd0-4dac-957c-6f02677dda57" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_dcc022e8-8264-4291-98ba-b98ddc4338ce" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_9fad4b4f-fdd0-4dac-957c-6f02677dda57" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_a2b2b8a3-ef48-40ff-a7d6-0473bc58171f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_9fad4b4f-fdd0-4dac-957c-6f02677dda57" xlink:to="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_a2b2b8a3-ef48-40ff-a7d6-0473bc58171f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_3029a0c4-ebc8-4b73-82e1-7c81acda2145" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_583edc3c-3835-4e90-a595-0f96ae5de906" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_3029a0c4-ebc8-4b73-82e1-7c81acda2145" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_3029a0c4-ebc8-4b73-82e1-7c81acda2145_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_3029a0c4-ebc8-4b73-82e1-7c81acda2145" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_3029a0c4-ebc8-4b73-82e1-7c81acda2145_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_3a300582-eada-4c03-9d45-8adfad3c3761" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_3029a0c4-ebc8-4b73-82e1-7c81acda2145" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_3a300582-eada-4c03-9d45-8adfad3c3761" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_EndoPredictMember_735b0729-009c-458c-9120-f9b0066fb2bb" xlink:href="mygn-20240630.xsd#mygn_EndoPredictMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_3a300582-eada-4c03-9d45-8adfad3c3761" xlink:to="loc_mygn_EndoPredictMember_735b0729-009c-458c-9120-f9b0066fb2bb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_69e27c17-34bf-468d-ac3b-e2a5a06311e1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_2a968fc7-0506-46d6-b97f-3f2b82c34a52" xlink:to="loc_us-gaap_LongTermDebtFairValue_69e27c17-34bf-468d-ac3b-e2a5a06311e1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf_13988820-f171-4d91-884c-050c45a5e16c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_2a968fc7-0506-46d6-b97f-3f2b82c34a52" xlink:to="loc_us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf_13988820-f171-4d91-884c-050c45a5e16c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_cdd78f38-dd51-40cc-938e-67d585a7cf73" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessCombinationContingentConsiderationLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_2a968fc7-0506-46d6-b97f-3f2b82c34a52" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_cdd78f38-dd51-40cc-938e-67d585a7cf73" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/FAIRVALUEMEASUREMENTSScheduleofFairValueofFinancialAssetsandLiabilitiesDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#FAIRVALUEMEASUREMENTSScheduleofFairValueofFinancialAssetsandLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/FAIRVALUEMEASUREMENTSScheduleofFairValueofFinancialAssetsandLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c417eaa2-2205-4fdb-bb2b-b9ea58fc2102" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c01dbb1f-980a-4895-9fdc-29be9a1bca76" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c417eaa2-2205-4fdb-bb2b-b9ea58fc2102" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c01dbb1f-980a-4895-9fdc-29be9a1bca76" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_934bc8a0-6697-48f3-b6c2-589a89bf6e7e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c01dbb1f-980a-4895-9fdc-29be9a1bca76" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_934bc8a0-6697-48f3-b6c2-589a89bf6e7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_934bc8a0-6697-48f3-b6c2-589a89bf6e7e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_934bc8a0-6697-48f3-b6c2-589a89bf6e7e" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_934bc8a0-6697-48f3-b6c2-589a89bf6e7e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7016e73d-0d64-44a4-946f-c85e78c7da62" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_934bc8a0-6697-48f3-b6c2-589a89bf6e7e" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7016e73d-0d64-44a4-946f-c85e78c7da62" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_0c2046ba-c4c2-4c13-888b-9da58fb22867" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7016e73d-0d64-44a4-946f-c85e78c7da62" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_0c2046ba-c4c2-4c13-888b-9da58fb22867" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_741a8645-734b-47e5-967b-1e1376e3e406" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7016e73d-0d64-44a4-946f-c85e78c7da62" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_741a8645-734b-47e5-967b-1e1376e3e406" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_0b05a4db-d46c-4f61-8b76-84dbf1553a56" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_7016e73d-0d64-44a4-946f-c85e78c7da62" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_0b05a4db-d46c-4f61-8b76-84dbf1553a56" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContingentConsiderationByTypeAxis_4bb5d632-39c6-4981-9e31-061aa4d5de29" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContingentConsiderationByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c01dbb1f-980a-4895-9fdc-29be9a1bca76" xlink:to="loc_us-gaap_ContingentConsiderationByTypeAxis_4bb5d632-39c6-4981-9e31-061aa4d5de29" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_4bb5d632-39c6-4981-9e31-061aa4d5de29_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContingentConsiderationTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_4bb5d632-39c6-4981-9e31-061aa4d5de29" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_4bb5d632-39c6-4981-9e31-061aa4d5de29_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_f74dac0e-c634-4b72-868c-0e8a1596725e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContingentConsiderationTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_4bb5d632-39c6-4981-9e31-061aa4d5de29" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_f74dac0e-c634-4b72-868c-0e8a1596725e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_ContingentConsiderationMember_612b459c-9805-4ad9-8967-2f813425e282" xlink:href="mygn-20240630.xsd#mygn_ContingentConsiderationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContingentConsiderationTypeDomain_f74dac0e-c634-4b72-868c-0e8a1596725e" xlink:to="loc_mygn_ContingentConsiderationMember_612b459c-9805-4ad9-8967-2f813425e282" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_ef680f42-1a89-47f8-8353-5b0516dcebcd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c01dbb1f-980a-4895-9fdc-29be9a1bca76" xlink:to="loc_us-gaap_FinancialInstrumentAxis_ef680f42-1a89-47f8-8353-5b0516dcebcd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ef680f42-1a89-47f8-8353-5b0516dcebcd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_ef680f42-1a89-47f8-8353-5b0516dcebcd" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ef680f42-1a89-47f8-8353-5b0516dcebcd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_28b3f39b-a3be-4ea0-b136-d197a471391f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_ef680f42-1a89-47f8-8353-5b0516dcebcd" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_28b3f39b-a3be-4ea0-b136-d197a471391f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_70eb7955-2312-4554-ac47-2225183e7946" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_28b3f39b-a3be-4ea0-b136-d197a471391f" xlink:to="loc_us-gaap_MoneyMarketFundsMember_70eb7955-2312-4554-ac47-2225183e7946" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_58abf072-618e-47b5-b7b0-e8c9730410bc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_28b3f39b-a3be-4ea0-b136-d197a471391f" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_58abf072-618e-47b5-b7b0-e8c9730410bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MunicipalBondsMember_92100ce2-1cf2-486f-96c5-77a61da4ff62" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_MunicipalBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_28b3f39b-a3be-4ea0-b136-d197a471391f" xlink:to="loc_us-gaap_MunicipalBondsMember_92100ce2-1cf2-486f-96c5-77a61da4ff62" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_0cd722fd-2b65-4fa5-a3ad-8c78a5b49110" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c417eaa2-2205-4fdb-bb2b-b9ea58fc2102" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_0cd722fd-2b65-4fa5-a3ad-8c78a5b49110" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_0674a03d-5443-4b17-8c80-9fb251b6af32" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c417eaa2-2205-4fdb-bb2b-b9ea58fc2102" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_0674a03d-5443-4b17-8c80-9fb251b6af32" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetAssetLiability_6e36188f-d23d-488d-812d-63b8d8ab593c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueNetAssetLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_c417eaa2-2205-4fdb-bb2b-b9ea58fc2102" xlink:to="loc_us-gaap_FairValueNetAssetLiability_6e36188f-d23d-488d-812d-63b8d8ab593c" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/PROPERTYPLANTANDEQUIPMENTNETScheduleofPropertyPlantandEquipmentNetDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#PROPERTYPLANTANDEQUIPMENTNETScheduleofPropertyPlantandEquipmentNetDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/PROPERTYPLANTANDEQUIPMENTNETScheduleofPropertyPlantandEquipmentNetDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_d4fa3dc4-be79-4b77-94a4-760e797175a0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_9d153e64-7070-4b36-8c96-1b2db4c93969" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_d4fa3dc4-be79-4b77-94a4-760e797175a0" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_9d153e64-7070-4b36-8c96-1b2db4c93969" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_a420fb42-60cf-4120-a87c-dc3f3bf541d4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_9d153e64-7070-4b36-8c96-1b2db4c93969" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_a420fb42-60cf-4120-a87c-dc3f3bf541d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_a420fb42-60cf-4120-a87c-dc3f3bf541d4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_a420fb42-60cf-4120-a87c-dc3f3bf541d4" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_a420fb42-60cf-4120-a87c-dc3f3bf541d4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_cb159755-7128-4cba-838b-2280ddec8921" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_a420fb42-60cf-4120-a87c-dc3f3bf541d4" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_cb159755-7128-4cba-838b-2280ddec8921" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_7fca5b4b-ff1b-4fac-b8f6-867c65b7c5c2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_cb159755-7128-4cba-838b-2280ddec8921" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_7fca5b4b-ff1b-4fac-b8f6-867c65b7c5c2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquipmentMember_bf9cbe6e-80aa-47f7-973a-17f3dbff82ef" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_cb159755-7128-4cba-838b-2280ddec8921" xlink:to="loc_us-gaap_EquipmentMember_bf9cbe6e-80aa-47f7-973a-17f3dbff82ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_5bb66454-d1bb-4990-8747-de84fecb1365" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_d4fa3dc4-be79-4b77-94a4-760e797175a0" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_5bb66454-d1bb-4990-8747-de84fecb1365" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_437165b2-0ee6-46be-bc00-db0fc13a0274" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_d4fa3dc4-be79-4b77-94a4-760e797175a0" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_437165b2-0ee6-46be-bc00-db0fc13a0274" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_PropertyPlantAndEquipmentNetBeforeReclassificationOfAssetsHeldForSale_1559d7ec-8462-4307-a700-575ed07cd1af" xlink:href="mygn-20240630.xsd#mygn_PropertyPlantAndEquipmentNetBeforeReclassificationOfAssetsHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_d4fa3dc4-be79-4b77-94a4-760e797175a0" xlink:to="loc_mygn_PropertyPlantAndEquipmentNetBeforeReclassificationOfAssetsHeldForSale_1559d7ec-8462-4307-a700-575ed07cd1af" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_PropertyPlantAndEquipmentNetReclassificationOfAssetsHeldForSale_994ca54d-63cd-4ed3-9b77-27c1c67100de" xlink:href="mygn-20240630.xsd#mygn_PropertyPlantAndEquipmentNetReclassificationOfAssetsHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_d4fa3dc4-be79-4b77-94a4-760e797175a0" xlink:to="loc_mygn_PropertyPlantAndEquipmentNetReclassificationOfAssetsHeldForSale_994ca54d-63cd-4ed3-9b77-27c1c67100de" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_e26eb1c8-d94c-471d-be38-361a542b271b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_d4fa3dc4-be79-4b77-94a4-760e797175a0" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_e26eb1c8-d94c-471d-be38-361a542b271b" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/PROPERTYPLANTANDEQUIPMENTNETNarrativeDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#PROPERTYPLANTANDEQUIPMENTNETNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/PROPERTYPLANTANDEQUIPMENTNETNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_489572db-cdc5-4759-b8ec-7d96321e7227" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_7ee0f51b-acd7-4ca1-8318-d3eea54d1508" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_489572db-cdc5-4759-b8ec-7d96321e7227" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_7ee0f51b-acd7-4ca1-8318-d3eea54d1508" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_306e89e1-6306-40cf-af0d-6713b0a85dac" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_7ee0f51b-acd7-4ca1-8318-d3eea54d1508" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_306e89e1-6306-40cf-af0d-6713b0a85dac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_306e89e1-6306-40cf-af0d-6713b0a85dac_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_306e89e1-6306-40cf-af0d-6713b0a85dac" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_306e89e1-6306-40cf-af0d-6713b0a85dac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2892562e-4c77-4700-a536-4afb5eb47b24" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_306e89e1-6306-40cf-af0d-6713b0a85dac" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2892562e-4c77-4700-a536-4afb5eb47b24" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_1a75cb05-c01d-45d8-b570-36e8e962a199" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2892562e-4c77-4700-a536-4afb5eb47b24" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_1a75cb05-c01d-45d8-b570-36e8e962a199" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveAcceleratedDepreciation_19b3aa8e-bd9d-48c4-979e-e22e9ef73654" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringReserveAcceleratedDepreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_489572db-cdc5-4759-b8ec-7d96321e7227" xlink:to="loc_us-gaap_RestructuringReserveAcceleratedDepreciation_19b3aa8e-bd9d-48c4-979e-e22e9ef73654" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/GOODWILLANDINTANGIBLEASSETSScheduleofIntangibleAssetsDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#GOODWILLANDINTANGIBLEASSETSScheduleofIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/GOODWILLANDINTANGIBLEASSETSScheduleofIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_mygn_IntangibleAssetsLineItems_18203d49-c058-4878-8009-2b810602f6b9" xlink:href="mygn-20240630.xsd#mygn_IntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_ScheduleOfIntangibleAssetsTable_b7c6e008-1c53-4429-9d65-4228210505d7" xlink:href="mygn-20240630.xsd#mygn_ScheduleOfIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_mygn_IntangibleAssetsLineItems_18203d49-c058-4878-8009-2b810602f6b9" xlink:to="loc_mygn_ScheduleOfIntangibleAssetsTable_b7c6e008-1c53-4429-9d65-4228210505d7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_de9de73c-65c2-43f6-8df6-21579c4cb71d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_mygn_ScheduleOfIntangibleAssetsTable_b7c6e008-1c53-4429-9d65-4228210505d7" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_de9de73c-65c2-43f6-8df6-21579c4cb71d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_de9de73c-65c2-43f6-8df6-21579c4cb71d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_de9de73c-65c2-43f6-8df6-21579c4cb71d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_de9de73c-65c2-43f6-8df6-21579c4cb71d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_8c1fc16f-7968-4c21-a525-7ef988f1d84c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_de9de73c-65c2-43f6-8df6-21579c4cb71d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_8c1fc16f-7968-4c21-a525-7ef988f1d84c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_67ee7827-7bc2-4b6f-a2bd-12410d3f07e2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_8c1fc16f-7968-4c21-a525-7ef988f1d84c" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_67ee7827-7bc2-4b6f-a2bd-12410d3f07e2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_c1d1ddc6-ea66-43a2-84f1-54047b4809db" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ComputerSoftwareIntangibleAssetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_8c1fc16f-7968-4c21-a525-7ef988f1d84c" xlink:to="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_c1d1ddc6-ea66-43a2-84f1-54047b4809db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_ComputerSoftwareInProcessIntangibleAssetMember_503e0a34-715b-4964-bbc7-3bafeb333bc9" xlink:href="mygn-20240630.xsd#mygn_ComputerSoftwareInProcessIntangibleAssetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_8c1fc16f-7968-4c21-a525-7ef988f1d84c" xlink:to="loc_mygn_ComputerSoftwareInProcessIntangibleAssetMember_503e0a34-715b-4964-bbc7-3bafeb333bc9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_6f627bd8-0ded-441e-a23e-2224ed4c06f1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_8c1fc16f-7968-4c21-a525-7ef988f1d84c" xlink:to="loc_us-gaap_CustomerRelationshipsMember_6f627bd8-0ded-441e-a23e-2224ed4c06f1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksMember_8c89c4d9-2014-4b0c-b300-e3a6319d58f9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TrademarksMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_8c1fc16f-7968-4c21-a525-7ef988f1d84c" xlink:to="loc_us-gaap_TrademarksMember_8c89c4d9-2014-4b0c-b300-e3a6319d58f9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_FiniteLivedIntangibleAssetsGrossBeforeReclassificationOfAssetsHeldForSale_515be83b-a0e6-4837-a543-64443649c664" xlink:href="mygn-20240630.xsd#mygn_FiniteLivedIntangibleAssetsGrossBeforeReclassificationOfAssetsHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mygn_IntangibleAssetsLineItems_18203d49-c058-4878-8009-2b810602f6b9" xlink:to="loc_mygn_FiniteLivedIntangibleAssetsGrossBeforeReclassificationOfAssetsHeldForSale_515be83b-a0e6-4837-a543-64443649c664" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_FiniteLivedIntangibleAssetsAccumulatedAmortizationBeforeReclassificationOfAssetsHeldForSale_9567b5de-3365-498f-a81e-94bb08dc055a" xlink:href="mygn-20240630.xsd#mygn_FiniteLivedIntangibleAssetsAccumulatedAmortizationBeforeReclassificationOfAssetsHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mygn_IntangibleAssetsLineItems_18203d49-c058-4878-8009-2b810602f6b9" xlink:to="loc_mygn_FiniteLivedIntangibleAssetsAccumulatedAmortizationBeforeReclassificationOfAssetsHeldForSale_9567b5de-3365-498f-a81e-94bb08dc055a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_FiniteLivedIntangibleAssetsNetBeforeReclassificationOfAssetsHeldForSale_a292e002-ac31-4e03-bcbb-32183a48c92b" xlink:href="mygn-20240630.xsd#mygn_FiniteLivedIntangibleAssetsNetBeforeReclassificationOfAssetsHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mygn_IntangibleAssetsLineItems_18203d49-c058-4878-8009-2b810602f6b9" xlink:to="loc_mygn_FiniteLivedIntangibleAssetsNetBeforeReclassificationOfAssetsHeldForSale_a292e002-ac31-4e03-bcbb-32183a48c92b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_FiniteLivedIntangibleAssetsGrossReclassificationOfAssetsHeldForSale_a9201327-0386-401e-ba1e-f5539415a7e7" xlink:href="mygn-20240630.xsd#mygn_FiniteLivedIntangibleAssetsGrossReclassificationOfAssetsHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mygn_IntangibleAssetsLineItems_18203d49-c058-4878-8009-2b810602f6b9" xlink:to="loc_mygn_FiniteLivedIntangibleAssetsGrossReclassificationOfAssetsHeldForSale_a9201327-0386-401e-ba1e-f5539415a7e7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_FiniteLivedIntangibleAssetsAccumulatedAmortizationReclassificationOfAssetsHeldForSale_2e51a961-0c09-45b0-8cb8-873237652fec" xlink:href="mygn-20240630.xsd#mygn_FiniteLivedIntangibleAssetsAccumulatedAmortizationReclassificationOfAssetsHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mygn_IntangibleAssetsLineItems_18203d49-c058-4878-8009-2b810602f6b9" xlink:to="loc_mygn_FiniteLivedIntangibleAssetsAccumulatedAmortizationReclassificationOfAssetsHeldForSale_2e51a961-0c09-45b0-8cb8-873237652fec" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_FiniteLivedIntangibleAssetsNetReclassificationOfAssetsHeldForSale_3bf03f06-669a-43e8-8778-be5d74e4836b" xlink:href="mygn-20240630.xsd#mygn_FiniteLivedIntangibleAssetsNetReclassificationOfAssetsHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mygn_IntangibleAssetsLineItems_18203d49-c058-4878-8009-2b810602f6b9" xlink:to="loc_mygn_FiniteLivedIntangibleAssetsNetReclassificationOfAssetsHeldForSale_3bf03f06-669a-43e8-8778-be5d74e4836b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_b261cca5-6bd4-4627-a3c5-ea571d79cb48" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mygn_IntangibleAssetsLineItems_18203d49-c058-4878-8009-2b810602f6b9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_b261cca5-6bd4-4627-a3c5-ea571d79cb48" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_7121d127-d791-4098-a926-b2f95774a503" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mygn_IntangibleAssetsLineItems_18203d49-c058-4878-8009-2b810602f6b9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_7121d127-d791-4098-a926-b2f95774a503" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_c8e9ffb8-0a09-4e6a-b328-3109cb1137de" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mygn_IntangibleAssetsLineItems_18203d49-c058-4878-8009-2b810602f6b9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_c8e9ffb8-0a09-4e6a-b328-3109cb1137de" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/LONGTERMDEBTDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#LONGTERMDEBTDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/LONGTERMDEBTDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_88bfef16-0c59-499d-8b2e-73c3c79457ef" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_us-gaap_DebtInstrumentTable_88bfef16-0c59-499d-8b2e-73c3c79457ef" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_954631f2-6736-4073-9563-7929729b8b8c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_88bfef16-0c59-499d-8b2e-73c3c79457ef" xlink:to="loc_us-gaap_CreditFacilityAxis_954631f2-6736-4073-9563-7929729b8b8c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_954631f2-6736-4073-9563-7929729b8b8c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_954631f2-6736-4073-9563-7929729b8b8c" xlink:to="loc_us-gaap_CreditFacilityDomain_954631f2-6736-4073-9563-7929729b8b8c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_fcc62052-4150-47b7-8d24-d5d4fb37b58e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_954631f2-6736-4073-9563-7929729b8b8c" xlink:to="loc_us-gaap_CreditFacilityDomain_fcc62052-4150-47b7-8d24-d5d4fb37b58e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_2b802273-71c0-406c-bb6f-65a0eac5f73e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_fcc62052-4150-47b7-8d24-d5d4fb37b58e" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_2b802273-71c0-406c-bb6f-65a0eac5f73e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_e6505d21-3ba0-4667-9efb-ef05c3e7a714" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_88bfef16-0c59-499d-8b2e-73c3c79457ef" xlink:to="loc_us-gaap_DebtInstrumentAxis_e6505d21-3ba0-4667-9efb-ef05c3e7a714" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_e6505d21-3ba0-4667-9efb-ef05c3e7a714_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_e6505d21-3ba0-4667-9efb-ef05c3e7a714" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_e6505d21-3ba0-4667-9efb-ef05c3e7a714_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_0b656282-d055-4a08-9a6c-5fe6e5eff1e7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_e6505d21-3ba0-4667-9efb-ef05c3e7a714" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_0b656282-d055-4a08-9a6c-5fe6e5eff1e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_ABLFacilityMember_9e8d9e50-d15a-43af-8f90-d1ad60fdc5f2" xlink:href="mygn-20240630.xsd#mygn_ABLFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0b656282-d055-4a08-9a6c-5fe6e5eff1e7" xlink:to="loc_mygn_ABLFacilityMember_9e8d9e50-d15a-43af-8f90-d1ad60fdc5f2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_25d1d9f9-311b-4040-8429-ab18481707b7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_88bfef16-0c59-499d-8b2e-73c3c79457ef" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_25d1d9f9-311b-4040-8429-ab18481707b7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_25d1d9f9-311b-4040-8429-ab18481707b7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_25d1d9f9-311b-4040-8429-ab18481707b7" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_25d1d9f9-311b-4040-8429-ab18481707b7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_7327f723-a6f0-4c16-b43d-fbc32a6cc258" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_25d1d9f9-311b-4040-8429-ab18481707b7" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_7327f723-a6f0-4c16-b43d-fbc32a6cc258" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_9cf33cca-218a-4257-a7b5-d65eb362055e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_7327f723-a6f0-4c16-b43d-fbc32a6cc258" xlink:to="loc_us-gaap_LineOfCreditMember_9cf33cca-218a-4257-a7b5-d65eb362055e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_27a2158b-d17f-43c6-bd73-e28ae5e20e3e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_88bfef16-0c59-499d-8b2e-73c3c79457ef" xlink:to="loc_us-gaap_VariableRateAxis_27a2158b-d17f-43c6-bd73-e28ae5e20e3e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_27a2158b-d17f-43c6-bd73-e28ae5e20e3e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_27a2158b-d17f-43c6-bd73-e28ae5e20e3e" xlink:to="loc_us-gaap_VariableRateDomain_27a2158b-d17f-43c6-bd73-e28ae5e20e3e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_10f719d8-77a2-4d72-a216-04f741af6e61" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_27a2158b-d17f-43c6-bd73-e28ae5e20e3e" xlink:to="loc_us-gaap_VariableRateDomain_10f719d8-77a2-4d72-a216-04f741af6e61" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_NewYorkFederalReserveBankRateMember_c9841f6c-5c5a-4cbb-b8b9-75eb7742862b" xlink:href="mygn-20240630.xsd#mygn_NewYorkFederalReserveBankRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_10f719d8-77a2-4d72-a216-04f741af6e61" xlink:to="loc_mygn_NewYorkFederalReserveBankRateMember_c9841f6c-5c5a-4cbb-b8b9-75eb7742862b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_288e4a1d-20fa-490f-b882-47b4bc886aec" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SecuredOvernightFinancingRateSofrMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_10f719d8-77a2-4d72-a216-04f741af6e61" xlink:to="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_288e4a1d-20fa-490f-b882-47b4bc886aec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_ABRFloorMember_8ee4f5a2-663f-452c-948c-0d049651b3c6" xlink:href="mygn-20240630.xsd#mygn_ABRFloorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_10f719d8-77a2-4d72-a216-04f741af6e61" xlink:to="loc_mygn_ABRFloorMember_8ee4f5a2-663f-452c-948c-0d049651b3c6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_57a2ed3e-f9b6-46f0-8f32-4f8e22687b71" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_88bfef16-0c59-499d-8b2e-73c3c79457ef" xlink:to="loc_srt_RangeAxis_57a2ed3e-f9b6-46f0-8f32-4f8e22687b71" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_57a2ed3e-f9b6-46f0-8f32-4f8e22687b71_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_57a2ed3e-f9b6-46f0-8f32-4f8e22687b71" xlink:to="loc_srt_RangeMember_57a2ed3e-f9b6-46f0-8f32-4f8e22687b71_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_533cf6ce-52c8-4350-a189-4e2842205d1a" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_57a2ed3e-f9b6-46f0-8f32-4f8e22687b71" xlink:to="loc_srt_RangeMember_533cf6ce-52c8-4350-a189-4e2842205d1a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_929a930c-7d56-4641-96a2-ffa40e19420b" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_533cf6ce-52c8-4350-a189-4e2842205d1a" xlink:to="loc_srt_MinimumMember_929a930c-7d56-4641-96a2-ffa40e19420b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_e6118674-421f-4771-9a0b-f7f61ae8b19e" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_533cf6ce-52c8-4350-a189-4e2842205d1a" xlink:to="loc_srt_MaximumMember_e6118674-421f-4771-9a0b-f7f61ae8b19e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_VariableRateScenarioAxis_801371b3-bdbe-4478-844d-04c8e352911f" xlink:href="mygn-20240630.xsd#mygn_VariableRateScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_88bfef16-0c59-499d-8b2e-73c3c79457ef" xlink:to="loc_mygn_VariableRateScenarioAxis_801371b3-bdbe-4478-844d-04c8e352911f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_VariableRateScenarioDomain_801371b3-bdbe-4478-844d-04c8e352911f_default" xlink:href="mygn-20240630.xsd#mygn_VariableRateScenarioDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_mygn_VariableRateScenarioAxis_801371b3-bdbe-4478-844d-04c8e352911f" xlink:to="loc_mygn_VariableRateScenarioDomain_801371b3-bdbe-4478-844d-04c8e352911f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_VariableRateScenarioDomain_1dbcf021-7447-4a8f-b8a2-104cdad19626" xlink:href="mygn-20240630.xsd#mygn_VariableRateScenarioDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_mygn_VariableRateScenarioAxis_801371b3-bdbe-4478-844d-04c8e352911f" xlink:to="loc_mygn_VariableRateScenarioDomain_1dbcf021-7447-4a8f-b8a2-104cdad19626" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_VariableRateScenarioOneMember_0cc9653c-0669-4623-8ec2-1405c9fb7073" xlink:href="mygn-20240630.xsd#mygn_VariableRateScenarioOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mygn_VariableRateScenarioDomain_1dbcf021-7447-4a8f-b8a2-104cdad19626" xlink:to="loc_mygn_VariableRateScenarioOneMember_0cc9653c-0669-4623-8ec2-1405c9fb7073" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_VariableRateScenarioTwoMember_44ca62aa-6edf-482f-a154-54a198de97c8" xlink:href="mygn-20240630.xsd#mygn_VariableRateScenarioTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mygn_VariableRateScenarioDomain_1dbcf021-7447-4a8f-b8a2-104cdad19626" xlink:to="loc_mygn_VariableRateScenarioTwoMember_44ca62aa-6edf-482f-a154-54a198de97c8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_0a400c59-f14c-4fb2-8bf7-813a9e64070d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_0a400c59-f14c-4fb2-8bf7-813a9e64070d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_LineOfCreditFacilityAccordionFeatureIncreaseLimit_13456531-e154-4857-a2e1-7ba551e91bd5" xlink:href="mygn-20240630.xsd#mygn_LineOfCreditFacilityAccordionFeatureIncreaseLimit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_mygn_LineOfCreditFacilityAccordionFeatureIncreaseLimit_13456531-e154-4857-a2e1-7ba551e91bd5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_c3c98715-edc7-4cc9-9478-f5a2389dc5ef" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_c3c98715-edc7-4cc9-9478-f5a2389dc5ef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_dd10ac24-b82d-4680-8a93-8e3c562c9048" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_us-gaap_LongTermDebt_dd10ac24-b82d-4680-8a93-8e3c562c9048" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_6bfe8764-9cf5-4f09-a3d7-688dc3ca655d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_6bfe8764-9cf5-4f09-a3d7-688dc3ca655d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_LineOfCreditFacilityBorrowingBasePercentOfEligibleAccountsReceivablePlusCertainCashHeld_759ec476-5a7e-4840-a0e6-cd3ac1d7e9f2" xlink:href="mygn-20240630.xsd#mygn_LineOfCreditFacilityBorrowingBasePercentOfEligibleAccountsReceivablePlusCertainCashHeld"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_mygn_LineOfCreditFacilityBorrowingBasePercentOfEligibleAccountsReceivablePlusCertainCashHeld_759ec476-5a7e-4840-a0e6-cd3ac1d7e9f2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_LineOfCreditFacilityBorrowingBaseEligibleCashHeld_c591dbd7-7e27-4567-bd50-16a1c0bd995c" xlink:href="mygn-20240630.xsd#mygn_LineOfCreditFacilityBorrowingBaseEligibleCashHeld"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_mygn_LineOfCreditFacilityBorrowingBaseEligibleCashHeld_c591dbd7-7e27-4567-bd50-16a1c0bd995c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_LineOfCreditFacilityBorrowingBaseEligibleCashCollectionsPeriod_e33dbc9d-ac55-4a77-8fe3-453f2a496ae7" xlink:href="mygn-20240630.xsd#mygn_LineOfCreditFacilityBorrowingBaseEligibleCashCollectionsPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_mygn_LineOfCreditFacilityBorrowingBaseEligibleCashCollectionsPeriod_e33dbc9d-ac55-4a77-8fe3-453f2a496ae7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_dd7488eb-f05d-4a6a-aa04-c448561b5ab7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_dd7488eb-f05d-4a6a-aa04-c448561b5ab7" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_DebtInstrumentFloorPercentage_fdcb751e-3726-4b8b-90b5-2b39a9205124" xlink:href="mygn-20240630.xsd#mygn_DebtInstrumentFloorPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_mygn_DebtInstrumentFloorPercentage_fdcb751e-3726-4b8b-90b5-2b39a9205124" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_b4c90d23-d276-446a-b021-15e101b35e70" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_b4c90d23-d276-446a-b021-15e101b35e70" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtWeightedAverageInterestRate_437a8b2d-1969-4182-825a-7f038214e38e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtWeightedAverageInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_us-gaap_DebtWeightedAverageInterestRate_437a8b2d-1969-4182-825a-7f038214e38e" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_DebtInstrumentCovenantLiquidityAmountMinimum_6f58878b-e987-4a90-852c-87d0d009e9ef" xlink:href="mygn-20240630.xsd#mygn_DebtInstrumentCovenantLiquidityAmountMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_mygn_DebtInstrumentCovenantLiquidityAmountMinimum_6f58878b-e987-4a90-852c-87d0d009e9ef" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_DebtInstrumentCovenantAvailabilityAmountMinimum_978d54b3-914a-4036-8c05-63768d353e8f" xlink:href="mygn-20240630.xsd#mygn_DebtInstrumentCovenantAvailabilityAmountMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_mygn_DebtInstrumentCovenantAvailabilityAmountMinimum_978d54b3-914a-4036-8c05-63768d353e8f" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_DebtInstrumentCovenantFixedChargeRatioMinimum_78289b32-23a4-47e3-a003-b31f3a7d8d69" xlink:href="mygn-20240630.xsd#mygn_DebtInstrumentCovenantFixedChargeRatioMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_mygn_DebtInstrumentCovenantFixedChargeRatioMinimum_78289b32-23a4-47e3-a003-b31f3a7d8d69" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeeAmount_31201cce-4a5a-439d-b34d-0104c2fb2f49" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityCommitmentFeeAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeeAmount_31201cce-4a5a-439d-b34d-0104c2fb2f49" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_843d4842-10b1-4cf9-bb93-44a424a09b23" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_843d4842-10b1-4cf9-bb93-44a424a09b23" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_LineOfCreditFacilityCommitmentFeeBorrowingBasePeriod_2d4009a4-65b1-44c1-8687-0e2bcb672204" xlink:href="mygn-20240630.xsd#mygn_LineOfCreditFacilityCommitmentFeeBorrowingBasePeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_mygn_LineOfCreditFacilityCommitmentFeeBorrowingBasePeriod_2d4009a4-65b1-44c1-8687-0e2bcb672204" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_LineOfCreditFacilityDebtDefaultAvailabilityThreshold_f383db90-92bc-4899-aef8-994d724c5403" xlink:href="mygn-20240630.xsd#mygn_LineOfCreditFacilityDebtDefaultAvailabilityThreshold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_mygn_LineOfCreditFacilityDebtDefaultAvailabilityThreshold_f383db90-92bc-4899-aef8-994d724c5403" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_DebtInstrumentDebtDefaultAvailabilityThresholdPercentageOfMaximumCommitmentAmount_db3fd058-457d-42d3-ad87-aa70fb480f88" xlink:href="mygn-20240630.xsd#mygn_DebtInstrumentDebtDefaultAvailabilityThresholdPercentageOfMaximumCommitmentAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_mygn_DebtInstrumentDebtDefaultAvailabilityThresholdPercentageOfMaximumCommitmentAmount_db3fd058-457d-42d3-ad87-aa70fb480f88" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_DebtInstrumentMaximumAmountBorrowingBasePeriod_39bfecb8-ed7c-403a-913f-38f00dfced05" xlink:href="mygn-20240630.xsd#mygn_DebtInstrumentMaximumAmountBorrowingBasePeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ee8a937f-96da-4a62-acac-665d01d1cbfe" xlink:to="loc_mygn_DebtInstrumentMaximumAmountBorrowingBasePeriod_39bfecb8-ed7c-403a-913f-38f00dfced05" xlink:type="arc" order="20"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/OTHERLONGTERMLIABILITIESNarrativeDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#OTHERLONGTERMLIABILITIESNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/OTHERLONGTERMLIABILITIESNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_1cd3f29c-6629-4eb7-9747-8410f27bb4f6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_73a14b26-5c65-401b-8987-37f92109c4d7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_1cd3f29c-6629-4eb7-9747-8410f27bb4f6" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_73a14b26-5c65-401b-8987-37f92109c4d7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_a34e161f-9f99-49aa-996e-6da1a762c484" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_73a14b26-5c65-401b-8987-37f92109c4d7" xlink:to="loc_srt_LitigationCaseAxis_a34e161f-9f99-49aa-996e-6da1a762c484" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_a34e161f-9f99-49aa-996e-6da1a762c484_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_a34e161f-9f99-49aa-996e-6da1a762c484" xlink:to="loc_srt_LitigationCaseTypeDomain_a34e161f-9f99-49aa-996e-6da1a762c484_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_9ff00558-6c0e-4c69-a2d2-c12e9250382a" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_a34e161f-9f99-49aa-996e-6da1a762c484" xlink:to="loc_srt_LitigationCaseTypeDomain_9ff00558-6c0e-4c69-a2d2-c12e9250382a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_RaygenIncVersusMyriadWomensHealthIncMember_09c022ea-3375-4e52-b2a0-8ab4c879ac27" xlink:href="mygn-20240630.xsd#mygn_RaygenIncVersusMyriadWomensHealthIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_9ff00558-6c0e-4c69-a2d2-c12e9250382a" xlink:to="loc_mygn_RaygenIncVersusMyriadWomensHealthIncMember_09c022ea-3375-4e52-b2a0-8ab4c879ac27" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusAxis_7e5df461-fed6-4128-9c76-146a7c5c05bf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_73a14b26-5c65-401b-8987-37f92109c4d7" xlink:to="loc_us-gaap_LitigationStatusAxis_7e5df461-fed6-4128-9c76-146a7c5c05bf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusDomain_7e5df461-fed6-4128-9c76-146a7c5c05bf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LitigationStatusAxis_7e5df461-fed6-4128-9c76-146a7c5c05bf" xlink:to="loc_us-gaap_LitigationStatusDomain_7e5df461-fed6-4128-9c76-146a7c5c05bf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusDomain_2522eafb-c2df-4fd8-8675-c41fb7076a5e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LitigationStatusAxis_7e5df461-fed6-4128-9c76-146a7c5c05bf" xlink:to="loc_us-gaap_LitigationStatusDomain_2522eafb-c2df-4fd8-8675-c41fb7076a5e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_SettledLitigationContingentPaymentsMember_fb682686-bb69-4aa7-8b2d-34269910e4b2" xlink:href="mygn-20240630.xsd#mygn_SettledLitigationContingentPaymentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LitigationStatusDomain_2522eafb-c2df-4fd8-8675-c41fb7076a5e" xlink:to="loc_mygn_SettledLitigationContingentPaymentsMember_fb682686-bb69-4aa7-8b2d-34269910e4b2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_SettledLitigationNonContingentPaymentsMember_95ace401-e73c-4ef3-afcd-951afc96e939" xlink:href="mygn-20240630.xsd#mygn_SettledLitigationNonContingentPaymentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LitigationStatusDomain_2522eafb-c2df-4fd8-8675-c41fb7076a5e" xlink:to="loc_mygn_SettledLitigationNonContingentPaymentsMember_95ace401-e73c-4ef3-afcd-951afc96e939" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_LitigationInstallmentsAxis_5829a3da-0f7e-4666-a2ff-56c23452ed56" xlink:href="mygn-20240630.xsd#mygn_LitigationInstallmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_73a14b26-5c65-401b-8987-37f92109c4d7" xlink:to="loc_mygn_LitigationInstallmentsAxis_5829a3da-0f7e-4666-a2ff-56c23452ed56" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_LitigationInstallmentsDomain_5829a3da-0f7e-4666-a2ff-56c23452ed56_default" xlink:href="mygn-20240630.xsd#mygn_LitigationInstallmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_mygn_LitigationInstallmentsAxis_5829a3da-0f7e-4666-a2ff-56c23452ed56" xlink:to="loc_mygn_LitigationInstallmentsDomain_5829a3da-0f7e-4666-a2ff-56c23452ed56_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_LitigationInstallmentsDomain_4509e1d4-d178-4817-905c-7b8107dbae32" xlink:href="mygn-20240630.xsd#mygn_LitigationInstallmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_mygn_LitigationInstallmentsAxis_5829a3da-0f7e-4666-a2ff-56c23452ed56" xlink:to="loc_mygn_LitigationInstallmentsDomain_4509e1d4-d178-4817-905c-7b8107dbae32" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_FirstInstallmentMember_fd0c1c75-d3ec-4677-b312-7cb57b224f2c" xlink:href="mygn-20240630.xsd#mygn_FirstInstallmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mygn_LitigationInstallmentsDomain_4509e1d4-d178-4817-905c-7b8107dbae32" xlink:to="loc_mygn_FirstInstallmentMember_fd0c1c75-d3ec-4677-b312-7cb57b224f2c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_SecondInstallmentMember_3380545b-496d-4924-881d-4a5cfad182b6" xlink:href="mygn-20240630.xsd#mygn_SecondInstallmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mygn_LitigationInstallmentsDomain_4509e1d4-d178-4817-905c-7b8107dbae32" xlink:to="loc_mygn_SecondInstallmentMember_3380545b-496d-4924-881d-4a5cfad182b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_ThirdInstallmentMember_ecbcad22-9aac-4207-8cb9-9d708d6eeffa" xlink:href="mygn-20240630.xsd#mygn_ThirdInstallmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mygn_LitigationInstallmentsDomain_4509e1d4-d178-4817-905c-7b8107dbae32" xlink:to="loc_mygn_ThirdInstallmentMember_ecbcad22-9aac-4207-8cb9-9d708d6eeffa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_FourthInstallmentMember_1f470ef9-e19f-4db3-b5be-ad3715487de3" xlink:href="mygn-20240630.xsd#mygn_FourthInstallmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mygn_LitigationInstallmentsDomain_4509e1d4-d178-4817-905c-7b8107dbae32" xlink:to="loc_mygn_FourthInstallmentMember_1f470ef9-e19f-4db3-b5be-ad3715487de3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_FifthInstallmentMember_a51321e9-f2c4-4d97-87cf-a77a3f51cf3d" xlink:href="mygn-20240630.xsd#mygn_FifthInstallmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mygn_LitigationInstallmentsDomain_4509e1d4-d178-4817-905c-7b8107dbae32" xlink:to="loc_mygn_FifthInstallmentMember_a51321e9-f2c4-4d97-87cf-a77a3f51cf3d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_92a23297-8944-4aa4-b179-e003cdf53faa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationSettlementAmountAwardedToOtherParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_1cd3f29c-6629-4eb7-9747-8410f27bb4f6" xlink:to="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_92a23297-8944-4aa4-b179-e003cdf53faa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_LitigationSettlementNumberOfInstallments_3fd699f9-7096-42c2-b170-ba69d65ab34c" xlink:href="mygn-20240630.xsd#mygn_LitigationSettlementNumberOfInstallments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_1cd3f29c-6629-4eb7-9747-8410f27bb4f6" xlink:to="loc_mygn_LitigationSettlementNumberOfInstallments_3fd699f9-7096-42c2-b170-ba69d65ab34c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_LitigationSettlementRemainingAmountAwardedToOtherParty_96b8a95f-2cbc-4641-ad88-7b0379269c0a" xlink:href="mygn-20240630.xsd#mygn_LitigationSettlementRemainingAmountAwardedToOtherParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_1cd3f29c-6629-4eb7-9747-8410f27bb4f6" xlink:to="loc_mygn_LitigationSettlementRemainingAmountAwardedToOtherParty_96b8a95f-2cbc-4641-ad88-7b0379269c0a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualCarryingValueCurrent_f6b67475-7f07-47b6-a39b-d20b882d3b82" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LossContingencyAccrualCarryingValueCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_1cd3f29c-6629-4eb7-9747-8410f27bb4f6" xlink:to="loc_us-gaap_LossContingencyAccrualCarryingValueCurrent_f6b67475-7f07-47b6-a39b-d20b882d3b82" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_LegalChargesPendingSettlementNoncurrent_057b7b39-0599-433d-9f88-2096c2f7e27c" xlink:href="mygn-20240630.xsd#mygn_LegalChargesPendingSettlementNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_1cd3f29c-6629-4eb7-9747-8410f27bb4f6" xlink:to="loc_mygn_LegalChargesPendingSettlementNoncurrent_057b7b39-0599-433d-9f88-2096c2f7e27c" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/STOCKBASEDCOMPENSATIONNarrativeDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#STOCKBASEDCOMPENSATIONNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/STOCKBASEDCOMPENSATIONNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1bd20482-784a-45a3-8142-88055b37eebb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_359ab193-bf21-4766-aa99-0e00939ee2b5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1bd20482-784a-45a3-8142-88055b37eebb" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_359ab193-bf21-4766-aa99-0e00939ee2b5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_b786cf4f-eb5d-43da-b9c1-cede033aea20" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_359ab193-bf21-4766-aa99-0e00939ee2b5" xlink:to="loc_us-gaap_AwardTypeAxis_b786cf4f-eb5d-43da-b9c1-cede033aea20" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b786cf4f-eb5d-43da-b9c1-cede033aea20_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_b786cf4f-eb5d-43da-b9c1-cede033aea20" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b786cf4f-eb5d-43da-b9c1-cede033aea20_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b27fa2b0-3d34-4ff5-b8e4-ed30c773020a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_b786cf4f-eb5d-43da-b9c1-cede033aea20" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b27fa2b0-3d34-4ff5-b8e4-ed30c773020a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_OptionsAndRestrictedStockUnitsMember_90ade3a3-1957-48d6-99bc-4b9b834000a0" xlink:href="mygn-20240630.xsd#mygn_OptionsAndRestrictedStockUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b27fa2b0-3d34-4ff5-b8e4-ed30c773020a" xlink:to="loc_mygn_OptionsAndRestrictedStockUnitsMember_90ade3a3-1957-48d6-99bc-4b9b834000a0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_5e9b15a1-e682-47c9-bcf5-b514bbcf605d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mygn_OptionsAndRestrictedStockUnitsMember_90ade3a3-1957-48d6-99bc-4b9b834000a0" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_5e9b15a1-e682-47c9-bcf5-b514bbcf605d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_48bce4ad-e037-49ee-9f0b-3311e1ee4c9d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mygn_OptionsAndRestrictedStockUnitsMember_90ade3a3-1957-48d6-99bc-4b9b834000a0" xlink:to="loc_us-gaap_EmployeeStockOptionMember_48bce4ad-e037-49ee-9f0b-3311e1ee4c9d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualAxis_13b59b9d-0dc8-44eb-b082-f2eb69000ac5" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_TitleOfIndividualAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_359ab193-bf21-4766-aa99-0e00939ee2b5" xlink:to="loc_srt_TitleOfIndividualAxis_13b59b9d-0dc8-44eb-b082-f2eb69000ac5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_13b59b9d-0dc8-44eb-b082-f2eb69000ac5_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_TitleOfIndividualAxis_13b59b9d-0dc8-44eb-b082-f2eb69000ac5" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_13b59b9d-0dc8-44eb-b082-f2eb69000ac5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_ef272c30-58cd-4dc8-a6a7-ab135795e03e" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_TitleOfIndividualAxis_13b59b9d-0dc8-44eb-b082-f2eb69000ac5" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_ef272c30-58cd-4dc8-a6a7-ab135795e03e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_NonEmployeeDirectorMember_631415e9-6507-4101-8b7e-3acfd0d97f3e" xlink:href="mygn-20240630.xsd#mygn_NonEmployeeDirectorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_ef272c30-58cd-4dc8-a6a7-ab135795e03e" xlink:to="loc_mygn_NonEmployeeDirectorMember_631415e9-6507-4101-8b7e-3acfd0d97f3e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingAxis_3b74774c-3445-4894-95ea-34ceb8654695" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VestingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_359ab193-bf21-4766-aa99-0e00939ee2b5" xlink:to="loc_us-gaap_VestingAxis_3b74774c-3445-4894-95ea-34ceb8654695" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_3b74774c-3445-4894-95ea-34ceb8654695_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VestingAxis_3b74774c-3445-4894-95ea-34ceb8654695" xlink:to="loc_us-gaap_VestingDomain_3b74774c-3445-4894-95ea-34ceb8654695_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_a95db1f2-90b3-4ddc-aa09-df99cb5dcfa3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VestingAxis_3b74774c-3445-4894-95ea-34ceb8654695" xlink:to="loc_us-gaap_VestingDomain_a95db1f2-90b3-4ddc-aa09-df99cb5dcfa3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_bba310df-41fb-4621-8f34-af83b7dcd291" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationAwardTrancheOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_a95db1f2-90b3-4ddc-aa09-df99cb5dcfa3" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_bba310df-41fb-4621-8f34-af83b7dcd291" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheThreeMember_bbb6615d-496a-41a3-8ea2-15427ab3413d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationAwardTrancheThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_a95db1f2-90b3-4ddc-aa09-df99cb5dcfa3" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheThreeMember_bbb6615d-496a-41a3-8ea2-15427ab3413d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheTwoMember_e6902bca-d7de-4cdd-8d98-86132822b663" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationAwardTrancheTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_a95db1f2-90b3-4ddc-aa09-df99cb5dcfa3" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheTwoMember_e6902bca-d7de-4cdd-8d98-86132822b663" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_14962dd0-f0bd-4b68-8846-35fa086d66ed" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_359ab193-bf21-4766-aa99-0e00939ee2b5" xlink:to="loc_us-gaap_PlanNameAxis_14962dd0-f0bd-4b68-8846-35fa086d66ed" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_14962dd0-f0bd-4b68-8846-35fa086d66ed_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_14962dd0-f0bd-4b68-8846-35fa086d66ed" xlink:to="loc_us-gaap_PlanNameDomain_14962dd0-f0bd-4b68-8846-35fa086d66ed_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_4cd992ad-5617-4f63-afaa-bb4f080729ca" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_14962dd0-f0bd-4b68-8846-35fa086d66ed" xlink:to="loc_us-gaap_PlanNameDomain_4cd992ad-5617-4f63-afaa-bb4f080729ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_TwoThousandSeventeenEmployeeDirectorAndConsultantEquityIncentivePlanMember_5273d31b-13fa-490a-b576-7e16bddd39ad" xlink:href="mygn-20240630.xsd#mygn_TwoThousandSeventeenEmployeeDirectorAndConsultantEquityIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_4cd992ad-5617-4f63-afaa-bb4f080729ca" xlink:to="loc_mygn_TwoThousandSeventeenEmployeeDirectorAndConsultantEquityIncentivePlanMember_5273d31b-13fa-490a-b576-7e16bddd39ad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_EmployeeStockPurchasePlanTwentyTwelveMember_04381988-b3c6-474a-bcd7-6dec2197d089" xlink:href="mygn-20240630.xsd#mygn_EmployeeStockPurchasePlanTwentyTwelveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_4cd992ad-5617-4f63-afaa-bb4f080729ca" xlink:to="loc_mygn_EmployeeStockPurchasePlanTwentyTwelveMember_04381988-b3c6-474a-bcd7-6dec2197d089" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_93c5d19d-b36d-4e5c-91dc-85a1ee244631" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_359ab193-bf21-4766-aa99-0e00939ee2b5" xlink:to="loc_srt_RangeAxis_93c5d19d-b36d-4e5c-91dc-85a1ee244631" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_93c5d19d-b36d-4e5c-91dc-85a1ee244631_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_93c5d19d-b36d-4e5c-91dc-85a1ee244631" xlink:to="loc_srt_RangeMember_93c5d19d-b36d-4e5c-91dc-85a1ee244631_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_044cd4c8-c59f-4beb-b2c6-df0405e94818" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_93c5d19d-b36d-4e5c-91dc-85a1ee244631" xlink:to="loc_srt_RangeMember_044cd4c8-c59f-4beb-b2c6-df0405e94818" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_5ce242eb-ce1b-4eae-a631-b0e7cf62311e" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_044cd4c8-c59f-4beb-b2c6-df0405e94818" xlink:to="loc_srt_MinimumMember_5ce242eb-ce1b-4eae-a631-b0e7cf62311e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_0dbfd5f2-28e5-4b5a-9a48-6d2a37ece515" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_044cd4c8-c59f-4beb-b2c6-df0405e94818" xlink:to="loc_srt_MaximumMember_0dbfd5f2-28e5-4b5a-9a48-6d2a37ece515" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_3aeca296-9c89-40dd-b897-f8becca24cbc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1bd20482-784a-45a3-8142-88055b37eebb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_3aeca296-9c89-40dd-b897-f8becca24cbc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_a21a2d98-d6c8-4f9f-8ce7-6c9afbbc5bb7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1bd20482-784a-45a3-8142-88055b37eebb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_a21a2d98-d6c8-4f9f-8ce7-6c9afbbc5bb7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_c6d00491-c442-4d71-8f07-0b66ad4c40f9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1bd20482-784a-45a3-8142-88055b37eebb" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_c6d00491-c442-4d71-8f07-0b66ad4c40f9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsAverageTradingDays_f7ffd8e5-a90b-4d45-a867-36660b9a3448" xlink:href="mygn-20240630.xsd#mygn_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsAverageTradingDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1bd20482-784a-45a3-8142-88055b37eebb" xlink:to="loc_mygn_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsAverageTradingDays_f7ffd8e5-a90b-4d45-a867-36660b9a3448" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_5de47b1b-ae02-42c5-8c0f-7b7c73308433" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1bd20482-784a-45a3-8142-88055b37eebb" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_5de47b1b-ae02-42c5-8c0f-7b7c73308433" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_204ae1a7-6026-4d10-b443-2bbb345d9684" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1bd20482-784a-45a3-8142-88055b37eebb" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_204ae1a7-6026-4d10-b443-2bbb345d9684" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_31a7c03c-7aed-4b8c-b843-611fa8ace042" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1bd20482-784a-45a3-8142-88055b37eebb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_31a7c03c-7aed-4b8c-b843-611fa8ace042" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_a29bd31e-a1bc-4053-9800-ee4fa1f41c25" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1bd20482-784a-45a3-8142-88055b37eebb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_a29bd31e-a1bc-4053-9800-ee4fa1f41c25" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployee_69f7f53e-ee6c-4885-9674-6ccadbf6dbfb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1bd20482-784a-45a3-8142-88055b37eebb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployee_69f7f53e-ee6c-4885-9674-6ccadbf6dbfb" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_fbbe945c-dcba-48f6-b93c-6582193e7fae" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1bd20482-784a-45a3-8142-88055b37eebb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_fbbe945c-dcba-48f6-b93c-6582193e7fae" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_46178d7d-1526-4e1c-820a-890d01d0ba0f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1bd20482-784a-45a3-8142-88055b37eebb" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_46178d7d-1526-4e1c-820a-890d01d0ba0f" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/STOCKBASEDCOMPENSATIONScheduleofRestrictedStockUnitActivityDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#STOCKBASEDCOMPENSATIONScheduleofRestrictedStockUnitActivityDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/STOCKBASEDCOMPENSATIONScheduleofRestrictedStockUnitActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_05a145c4-c566-4384-a1f5-95267dab6b7b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_7e57b452-4a9a-4970-86bd-e488322a051b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_05a145c4-c566-4384-a1f5-95267dab6b7b" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_7e57b452-4a9a-4970-86bd-e488322a051b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_873359cb-ce06-4f6f-a369-1a78404c16d5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_7e57b452-4a9a-4970-86bd-e488322a051b" xlink:to="loc_us-gaap_AwardTypeAxis_873359cb-ce06-4f6f-a369-1a78404c16d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_873359cb-ce06-4f6f-a369-1a78404c16d5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_873359cb-ce06-4f6f-a369-1a78404c16d5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_873359cb-ce06-4f6f-a369-1a78404c16d5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0f30bf6c-ac55-424e-9f3b-15bd267c3242" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_873359cb-ce06-4f6f-a369-1a78404c16d5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0f30bf6c-ac55-424e-9f3b-15bd267c3242" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_f5528028-8e6c-409a-b26d-e4c155dc0604" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0f30bf6c-ac55-424e-9f3b-15bd267c3242" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_f5528028-8e6c-409a-b26d-e4c155dc0604" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_322637f4-0ce8-48a3-85ef-ceee84ddc6a1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_05a145c4-c566-4384-a1f5-95267dab6b7b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_322637f4-0ce8-48a3-85ef-ceee84ddc6a1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_008cf0ff-8814-4728-bd59-a7a895c99216" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_322637f4-0ce8-48a3-85ef-ceee84ddc6a1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_008cf0ff-8814-4728-bd59-a7a895c99216" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_71f62b08-595b-430a-8502-667f1fc42857" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_322637f4-0ce8-48a3-85ef-ceee84ddc6a1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_71f62b08-595b-430a-8502-667f1fc42857" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_83b2d307-19b1-4e86-9a01-cfe160120144" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_322637f4-0ce8-48a3-85ef-ceee84ddc6a1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_83b2d307-19b1-4e86-9a01-cfe160120144" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_0f32d988-9628-400e-a084-6c55e0bed2ad" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_322637f4-0ce8-48a3-85ef-ceee84ddc6a1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_0f32d988-9628-400e-a084-6c55e0bed2ad" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_2a74ac5f-10c3-41cd-8bc1-27618bc16bca" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_83343311-c37d-4f2f-9982-76728466c0a0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_05a145c4-c566-4384-a1f5-95267dab6b7b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_83343311-c37d-4f2f-9982-76728466c0a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_0b6238ef-b181-45fb-9aea-f98f87ccd94f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_83343311-c37d-4f2f-9982-76728466c0a0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_0b6238ef-b181-45fb-9aea-f98f87ccd94f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_f9052b61-206f-4a33-80e3-af80f5ab3a28" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_83343311-c37d-4f2f-9982-76728466c0a0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_f9052b61-206f-4a33-80e3-af80f5ab3a28" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_fa9d3491-6d87-47f2-a5ec-0615e02f5ef0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_83343311-c37d-4f2f-9982-76728466c0a0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_fa9d3491-6d87-47f2-a5ec-0615e02f5ef0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_c3f4171a-1b56-4caa-82ff-a7d6ea6569e3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_83343311-c37d-4f2f-9982-76728466c0a0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_c3f4171a-1b56-4caa-82ff-a7d6ea6569e3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_390498d2-b951-4f0e-99b3-a446865f2acb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/STOCKBASEDCOMPENSATIONScheduleofShareBasedCompensationEmployeeStockPurchasePlanActivityDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#STOCKBASEDCOMPENSATIONScheduleofShareBasedCompensationEmployeeStockPurchasePlanActivityDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/STOCKBASEDCOMPENSATIONScheduleofShareBasedCompensationEmployeeStockPurchasePlanActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_24f65b2d-53c2-49db-8b55-b3d0d48c7a5a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_31dcff30-fa33-4ae5-bb96-1ef01fae4a46" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_24f65b2d-53c2-49db-8b55-b3d0d48c7a5a" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_31dcff30-fa33-4ae5-bb96-1ef01fae4a46" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_a1210501-424c-4258-bc3f-9040438eb998" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_31dcff30-fa33-4ae5-bb96-1ef01fae4a46" xlink:to="loc_us-gaap_PlanNameAxis_a1210501-424c-4258-bc3f-9040438eb998" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_a1210501-424c-4258-bc3f-9040438eb998_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_a1210501-424c-4258-bc3f-9040438eb998" xlink:to="loc_us-gaap_PlanNameDomain_a1210501-424c-4258-bc3f-9040438eb998_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_6ab14076-1bde-4ea9-a3be-e25ed5a27717" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_a1210501-424c-4258-bc3f-9040438eb998" xlink:to="loc_us-gaap_PlanNameDomain_6ab14076-1bde-4ea9-a3be-e25ed5a27717" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_EmployeeStockPurchasePlanTwentyTwelveMember_bc165f08-8e5f-435f-8350-7ca48e9005b9" xlink:href="mygn-20240630.xsd#mygn_EmployeeStockPurchasePlanTwentyTwelveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_6ab14076-1bde-4ea9-a3be-e25ed5a27717" xlink:to="loc_mygn_EmployeeStockPurchasePlanTwentyTwelveMember_bc165f08-8e5f-435f-8350-7ca48e9005b9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesPurchasedForAward_48f9cce3-f662-40ab-a01b-0e5c1655ab50" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesPurchasedForAward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_24f65b2d-53c2-49db-8b55-b3d0d48c7a5a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesPurchasedForAward_48f9cce3-f662-40ab-a01b-0e5c1655ab50" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardCompensationCost1_290e4821-73dd-42bd-b34f-1a1d2a959637" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardCompensationCost1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_24f65b2d-53c2-49db-8b55-b3d0d48c7a5a" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardCompensationCost1_290e4821-73dd-42bd-b34f-1a1d2a959637" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/STOCKBASEDCOMPENSATIONScheduleofStockBasedCompensationExpenseDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#STOCKBASEDCOMPENSATIONScheduleofStockBasedCompensationExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/STOCKBASEDCOMPENSATIONScheduleofStockBasedCompensationExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_5f66e062-099f-48bf-90f3-c29c3852cb5a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_0b11e67a-519c-453f-b64d-8f468cc309ff" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_5f66e062-099f-48bf-90f3-c29c3852cb5a" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_0b11e67a-519c-453f-b64d-8f468cc309ff" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_6dcd78a4-79ca-4035-b94e-a3ea8f49214a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_0b11e67a-519c-453f-b64d-8f468cc309ff" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_6dcd78a4-79ca-4035-b94e-a3ea8f49214a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_6dcd78a4-79ca-4035-b94e-a3ea8f49214a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_6dcd78a4-79ca-4035-b94e-a3ea8f49214a" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_6dcd78a4-79ca-4035-b94e-a3ea8f49214a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_dacb085b-2297-4950-ba3b-c591a4c5b9a6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_6dcd78a4-79ca-4035-b94e-a3ea8f49214a" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_dacb085b-2297-4950-ba3b-c591a4c5b9a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_847f3bf2-e8bc-405e-8216-7eeb5112c249" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_dacb085b-2297-4950-ba3b-c591a4c5b9a6" xlink:to="loc_us-gaap_CostOfSalesMember_847f3bf2-e8bc-405e-8216-7eeb5112c249" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_9e5a6fea-b8df-4dd0-b2be-7ec7bbcf8f7c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_dacb085b-2297-4950-ba3b-c591a4c5b9a6" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_9e5a6fea-b8df-4dd0-b2be-7ec7bbcf8f7c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_5f2f4005-cfaf-48e9-9033-346415f40890" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_dacb085b-2297-4950-ba3b-c591a4c5b9a6" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_5f2f4005-cfaf-48e9-9033-346415f40890" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_9c0fc74a-5eab-4b31-bfbb-b8dbc1871853" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_5f66e062-099f-48bf-90f3-c29c3852cb5a" xlink:to="loc_us-gaap_ShareBasedCompensation_9c0fc74a-5eab-4b31-bfbb-b8dbc1871853" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/COMMITMENTSANDCONTINGENCIESDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#COMMITMENTSANDCONTINGENCIESDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/COMMITMENTSANDCONTINGENCIESDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_515e8767-0962-41d0-8e18-7d655e6ea217" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_c7232e7d-8e5d-4470-b21c-885bd20bd9a4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_515e8767-0962-41d0-8e18-7d655e6ea217" xlink:to="loc_us-gaap_LossContingenciesTable_c7232e7d-8e5d-4470-b21c-885bd20bd9a4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusAxis_edcfcb2c-d9ca-43c3-bb4f-4f302e82740e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_c7232e7d-8e5d-4470-b21c-885bd20bd9a4" xlink:to="loc_us-gaap_LitigationStatusAxis_edcfcb2c-d9ca-43c3-bb4f-4f302e82740e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusDomain_edcfcb2c-d9ca-43c3-bb4f-4f302e82740e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LitigationStatusAxis_edcfcb2c-d9ca-43c3-bb4f-4f302e82740e" xlink:to="loc_us-gaap_LitigationStatusDomain_edcfcb2c-d9ca-43c3-bb4f-4f302e82740e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusDomain_4a43c547-fa0f-4b37-b17b-34d1eecd765f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LitigationStatusAxis_edcfcb2c-d9ca-43c3-bb4f-4f302e82740e" xlink:to="loc_us-gaap_LitigationStatusDomain_4a43c547-fa0f-4b37-b17b-34d1eecd765f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PendingLitigationMember_ec0592fa-700c-4f7c-adfe-4ebd1604d271" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PendingLitigationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LitigationStatusDomain_4a43c547-fa0f-4b37-b17b-34d1eecd765f" xlink:to="loc_us-gaap_PendingLitigationMember_ec0592fa-700c-4f7c-adfe-4ebd1604d271" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_9369a6cc-b9d4-4911-a5ea-761bf1bc1137" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_c7232e7d-8e5d-4470-b21c-885bd20bd9a4" xlink:to="loc_srt_RangeAxis_9369a6cc-b9d4-4911-a5ea-761bf1bc1137" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_9369a6cc-b9d4-4911-a5ea-761bf1bc1137_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_9369a6cc-b9d4-4911-a5ea-761bf1bc1137" xlink:to="loc_srt_RangeMember_9369a6cc-b9d4-4911-a5ea-761bf1bc1137_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_00065cbc-362b-4253-bcab-0bff216804a2" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_9369a6cc-b9d4-4911-a5ea-761bf1bc1137" xlink:to="loc_srt_RangeMember_00065cbc-362b-4253-bcab-0bff216804a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_7052f217-b5b0-45dd-965f-668f1565eea5" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_00065cbc-362b-4253-bcab-0bff216804a2" xlink:to="loc_srt_MaximumMember_7052f217-b5b0-45dd-965f-668f1565eea5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_954d5f2b-12b6-4d28-b484-68381d1e6ab8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_c7232e7d-8e5d-4470-b21c-885bd20bd9a4" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_954d5f2b-12b6-4d28-b484-68381d1e6ab8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_954d5f2b-12b6-4d28-b484-68381d1e6ab8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_954d5f2b-12b6-4d28-b484-68381d1e6ab8" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_954d5f2b-12b6-4d28-b484-68381d1e6ab8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_8a89ed93-1029-4c7d-94a9-4be7f6987aca" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_954d5f2b-12b6-4d28-b484-68381d1e6ab8" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_8a89ed93-1029-4c7d-94a9-4be7f6987aca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_c12759ab-23f4-44fb-b2fb-17770280d80c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_8a89ed93-1029-4c7d-94a9-4be7f6987aca" xlink:to="loc_us-gaap_SubsequentEventMember_c12759ab-23f4-44fb-b2fb-17770280d80c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_9907936f-946f-43bc-8267-84ad991bfd8d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationSettlementAmountAwardedToOtherParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_515e8767-0962-41d0-8e18-7d655e6ea217" xlink:to="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_9907936f-946f-43bc-8267-84ad991bfd8d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationReserveCurrent_2b37ad2a-2b92-4922-a8c6-7500528666d5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationReserveCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_515e8767-0962-41d0-8e18-7d655e6ea217" xlink:to="loc_us-gaap_LitigationReserveCurrent_2b37ad2a-2b92-4922-a8c6-7500528666d5" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/LEASESDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#LEASESDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/LEASESDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_837287e0-3101-4ab7-b5ae-c53238a68526" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_87d7bb1f-6897-4915-95ae-72bd043dfc19" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_837287e0-3101-4ab7-b5ae-c53238a68526" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_87d7bb1f-6897-4915-95ae-72bd043dfc19" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_730fb333-b3b8-480a-9e80-fbc6cbf7b1a1" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_87d7bb1f-6897-4915-95ae-72bd043dfc19" xlink:to="loc_srt_RangeAxis_730fb333-b3b8-480a-9e80-fbc6cbf7b1a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_730fb333-b3b8-480a-9e80-fbc6cbf7b1a1_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_730fb333-b3b8-480a-9e80-fbc6cbf7b1a1" xlink:to="loc_srt_RangeMember_730fb333-b3b8-480a-9e80-fbc6cbf7b1a1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_a26436c1-ccbd-472e-a202-b1d4db14ca87" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_730fb333-b3b8-480a-9e80-fbc6cbf7b1a1" xlink:to="loc_srt_RangeMember_a26436c1-ccbd-472e-a202-b1d4db14ca87" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_de58fb74-816a-429e-a91f-39a367cd2928" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_a26436c1-ccbd-472e-a202-b1d4db14ca87" xlink:to="loc_srt_MinimumMember_de58fb74-816a-429e-a91f-39a367cd2928" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_7ef5fef3-9379-4d31-930c-7b79a42d1c45" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_a26436c1-ccbd-472e-a202-b1d4db14ca87" xlink:to="loc_srt_MaximumMember_7ef5fef3-9379-4d31-930c-7b79a42d1c45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_3bb9f382-8d59-4473-b6e8-cf7b76ab3875" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_87d7bb1f-6897-4915-95ae-72bd043dfc19" xlink:to="loc_srt_StatementGeographicalAxis_3bb9f382-8d59-4473-b6e8-cf7b76ab3875" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_3bb9f382-8d59-4473-b6e8-cf7b76ab3875_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_3bb9f382-8d59-4473-b6e8-cf7b76ab3875" xlink:to="loc_srt_SegmentGeographicalDomain_3bb9f382-8d59-4473-b6e8-cf7b76ab3875_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_0f34a86c-c8ec-4802-a770-29d2d3ddc658" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_3bb9f382-8d59-4473-b6e8-cf7b76ab3875" xlink:to="loc_srt_SegmentGeographicalDomain_0f34a86c-c8ec-4802-a770-29d2d3ddc658" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_WestSaltLakeCityMember_4083e3bf-da97-46a6-8024-6d9f3ee9aee6" xlink:href="mygn-20240630.xsd#mygn_WestSaltLakeCityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_0f34a86c-c8ec-4802-a770-29d2d3ddc658" xlink:to="loc_mygn_WestSaltLakeCityMember_4083e3bf-da97-46a6-8024-6d9f3ee9aee6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_339e1ff1-99ab-45d1-aad4-a99613a8200a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_87d7bb1f-6897-4915-95ae-72bd043dfc19" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_339e1ff1-99ab-45d1-aad4-a99613a8200a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_339e1ff1-99ab-45d1-aad4-a99613a8200a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_339e1ff1-99ab-45d1-aad4-a99613a8200a" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_339e1ff1-99ab-45d1-aad4-a99613a8200a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_1032e115-9760-45ab-9565-fbdf257571f5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_339e1ff1-99ab-45d1-aad4-a99613a8200a" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_1032e115-9760-45ab-9565-fbdf257571f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_bcdad6c8-e97e-4b8d-ae37-9beb1afc000e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_1032e115-9760-45ab-9565-fbdf257571f5" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_bcdad6c8-e97e-4b8d-ae37-9beb1afc000e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_256ac0ec-ace1-4101-a922-1e2cb6a9c3fb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LesseeOperatingLeaseRemainingLeaseTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_837287e0-3101-4ab7-b5ae-c53238a68526" xlink:to="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_256ac0ec-ace1-4101-a922-1e2cb6a9c3fb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_92c727cf-e533-4254-9872-1c050567ca58" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_837287e0-3101-4ab7-b5ae-c53238a68526" xlink:to="loc_us-gaap_OperatingLeaseLiability_92c727cf-e533-4254-9872-1c050567ca58" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_9e69fa6a-e9e4-4641-800e-ee6c180435e6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_837287e0-3101-4ab7-b5ae-c53238a68526" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_9e69fa6a-e9e4-4641-800e-ee6c180435e6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_OperatingLeaseLiabilityCurrentTerminated_70f816a1-63b0-42aa-9187-b4c772b1478c" xlink:href="mygn-20240630.xsd#mygn_OperatingLeaseLiabilityCurrentTerminated"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_837287e0-3101-4ab7-b5ae-c53238a68526" xlink:to="loc_mygn_OperatingLeaseLiabilityCurrentTerminated_70f816a1-63b0-42aa-9187-b4c772b1478c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnTerminationOfLease_6c528766-edff-40be-a001-82e421957f5e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GainLossOnTerminationOfLease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_837287e0-3101-4ab7-b5ae-c53238a68526" xlink:to="loc_us-gaap_GainLossOnTerminationOfLease_6c528766-edff-40be-a001-82e421957f5e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AreaOfRealEstateProperty_bb2f9318-4710-462d-b84a-7ce36cdd3945" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AreaOfRealEstateProperty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_837287e0-3101-4ab7-b5ae-c53238a68526" xlink:to="loc_us-gaap_AreaOfRealEstateProperty_bb2f9318-4710-462d-b84a-7ce36cdd3945" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseTermOfContract_5744eb4a-4367-4161-8923-ed51fbec8758" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LesseeOperatingLeaseTermOfContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_837287e0-3101-4ab7-b5ae-c53238a68526" xlink:to="loc_us-gaap_LesseeOperatingLeaseTermOfContract_5744eb4a-4367-4161-8923-ed51fbec8758" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_f7110f3e-ce9f-417b-8107-2e074f1f570a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_837287e0-3101-4ab7-b5ae-c53238a68526" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_f7110f3e-ce9f-417b-8107-2e074f1f570a" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/ACCUMULATEDOTHERCOMPREHENSIVELOSSDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#ACCUMULATEDOTHERCOMPREHENSIVELOSSDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/ACCUMULATEDOTHERCOMPREHENSIVELOSSDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_5bf73711-bc6c-4c35-b1fa-cda3030d038f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_471bf6f5-6c2b-49cd-bcca-9c11cbd478a0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_5bf73711-bc6c-4c35-b1fa-cda3030d038f" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_471bf6f5-6c2b-49cd-bcca-9c11cbd478a0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_9b91135c-04d1-4e57-945a-096f1a41b48b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_471bf6f5-6c2b-49cd-bcca-9c11cbd478a0" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_9b91135c-04d1-4e57-945a-096f1a41b48b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_9b91135c-04d1-4e57-945a-096f1a41b48b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_9b91135c-04d1-4e57-945a-096f1a41b48b" xlink:to="loc_us-gaap_EquityComponentDomain_9b91135c-04d1-4e57-945a-096f1a41b48b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_97b6d4b7-bbed-4701-a541-75fdb0c0bc2d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_9b91135c-04d1-4e57-945a-096f1a41b48b" xlink:to="loc_us-gaap_EquityComponentDomain_97b6d4b7-bbed-4701-a541-75fdb0c0bc2d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_b1b26d26-b47f-4bff-bf4d-7b230de40d90" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_97b6d4b7-bbed-4701-a541-75fdb0c0bc2d" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_b1b26d26-b47f-4bff-bf4d-7b230de40d90" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_9688f8a5-98c4-415a-a190-b520d9871c27" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_5bf73711-bc6c-4c35-b1fa-cda3030d038f" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_9688f8a5-98c4-415a-a190-b520d9871c27" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_72b4951a-b2bb-4c08-9aa5-c8b0524d4822" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_9688f8a5-98c4-415a-a190-b520d9871c27" xlink:to="loc_us-gaap_StockholdersEquity_72b4951a-b2bb-4c08-9aa5-c8b0524d4822" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_78ca7728-9941-433f-9f18-1f3ece24563e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_9688f8a5-98c4-415a-a190-b520d9871c27" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_78ca7728-9941-433f-9f18-1f3ece24563e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentFromAOCIRealizedUponSaleOrLiquidationNetOfTax_0b52e20b-4361-40e8-9870-30d25e9270f2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentFromAOCIRealizedUponSaleOrLiquidationNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_9688f8a5-98c4-415a-a190-b520d9871c27" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentFromAOCIRealizedUponSaleOrLiquidationNetOfTax_0b52e20b-4361-40e8-9870-30d25e9270f2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_a2c4297c-4eda-4ff1-89f1-c30983fe1933" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/ASSETSANDLIABILITIESHELDFORSALENarrativeDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#ASSETSANDLIABILITIESHELDFORSALENarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/ASSETSANDLIABILITIESHELDFORSALENarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_24f0bb06-357b-4dc2-8a78-4afc821f8493" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_ab2ebf01-be9f-4738-8b2e-2453c03ff625" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_24f0bb06-357b-4dc2-8a78-4afc821f8493" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_ab2ebf01-be9f-4738-8b2e-2453c03ff625" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_9c970ba6-fb44-4995-8f78-1ce67b9d34b7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_ab2ebf01-be9f-4738-8b2e-2453c03ff625" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_9c970ba6-fb44-4995-8f78-1ce67b9d34b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_9c970ba6-fb44-4995-8f78-1ce67b9d34b7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_9c970ba6-fb44-4995-8f78-1ce67b9d34b7" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_9c970ba6-fb44-4995-8f78-1ce67b9d34b7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_11bb9aa5-3d8e-4d29-9e9f-802a3e98490c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_9c970ba6-fb44-4995-8f78-1ce67b9d34b7" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_11bb9aa5-3d8e-4d29-9e9f-802a3e98490c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_129c2d9d-325a-4a4f-8d3d-9f93c43ddf46" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_11bb9aa5-3d8e-4d29-9e9f-802a3e98490c" xlink:to="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_129c2d9d-325a-4a4f-8d3d-9f93c43ddf46" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_62c4bd9f-4ff6-45fb-9872-b8c2d95be4ae" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_ab2ebf01-be9f-4738-8b2e-2453c03ff625" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_62c4bd9f-4ff6-45fb-9872-b8c2d95be4ae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_62c4bd9f-4ff6-45fb-9872-b8c2d95be4ae_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_62c4bd9f-4ff6-45fb-9872-b8c2d95be4ae" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_62c4bd9f-4ff6-45fb-9872-b8c2d95be4ae_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_7d50e5da-ddae-4140-a434-a8b0c32eb0f6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_62c4bd9f-4ff6-45fb-9872-b8c2d95be4ae" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_7d50e5da-ddae-4140-a434-a8b0c32eb0f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_EndoPredictMember_3f76b497-f417-4258-b243-42ee09c46a9c" xlink:href="mygn-20240630.xsd#mygn_EndoPredictMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_7d50e5da-ddae-4140-a434-a8b0c32eb0f6" xlink:to="loc_mygn_EndoPredictMember_3f76b497-f417-4258-b243-42ee09c46a9c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_1b8b732a-c86e-47e5-8e38-0458cb49abd1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProceedsFromDivestitureOfBusinesses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_24f0bb06-357b-4dc2-8a78-4afc821f8493" xlink:to="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_1b8b732a-c86e-47e5-8e38-0458cb49abd1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf_779f5926-1ee5-4d2c-8b96-1a0c55a9e697" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_24f0bb06-357b-4dc2-8a78-4afc821f8493" xlink:to="loc_us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf_779f5926-1ee5-4d2c-8b96-1a0c55a9e697" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.myriad.com/role/ASSETSANDLIABILITIESHELDFORSALEScheduleDetails" xlink:type="simple" xlink:href="mygn-20240630.xsd#ASSETSANDLIABILITIESHELDFORSALEScheduleDetails"/>
  <link:definitionLink xlink:role="http://www.myriad.com/role/ASSETSANDLIABILITIESHELDFORSALEScheduleDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_13688a4f-0c21-4dfb-a3d3-46926e6e5f5e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_badc1a06-1674-4fb0-953f-7552e517efe3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_13688a4f-0c21-4dfb-a3d3-46926e6e5f5e" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_badc1a06-1674-4fb0-953f-7552e517efe3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_cab9aaba-70c6-4cb8-8efa-8cec3fb27a7f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_badc1a06-1674-4fb0-953f-7552e517efe3" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_cab9aaba-70c6-4cb8-8efa-8cec3fb27a7f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_cab9aaba-70c6-4cb8-8efa-8cec3fb27a7f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_cab9aaba-70c6-4cb8-8efa-8cec3fb27a7f" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_cab9aaba-70c6-4cb8-8efa-8cec3fb27a7f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_3bff4166-6f9c-4d8d-8a16-73ac1b923c08" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_cab9aaba-70c6-4cb8-8efa-8cec3fb27a7f" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_3bff4166-6f9c-4d8d-8a16-73ac1b923c08" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_fca22c42-067b-4df5-8bb9-de5fcdc8c1d6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_3bff4166-6f9c-4d8d-8a16-73ac1b923c08" xlink:to="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_fca22c42-067b-4df5-8bb9-de5fcdc8c1d6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_d52063ac-123a-4367-b67a-5792c91a5c50" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_badc1a06-1674-4fb0-953f-7552e517efe3" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_d52063ac-123a-4367-b67a-5792c91a5c50" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_d52063ac-123a-4367-b67a-5792c91a5c50_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_d52063ac-123a-4367-b67a-5792c91a5c50" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_d52063ac-123a-4367-b67a-5792c91a5c50_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_785d896e-9325-401c-a079-92f3a93f97ee" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_d52063ac-123a-4367-b67a-5792c91a5c50" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_785d896e-9325-401c-a079-92f3a93f97ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_EndoPredictMember_5fa26a04-dc8b-43e8-8851-11992e5e023c" xlink:href="mygn-20240630.xsd#mygn_EndoPredictMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_785d896e-9325-401c-a079-92f3a93f97ee" xlink:to="loc_mygn_EndoPredictMember_5fa26a04-dc8b-43e8-8851-11992e5e023c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationAbstract_779a872e-575a-4e91-a772-11ecc806a5f8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_13688a4f-0c21-4dfb-a3d3-46926e6e5f5e" xlink:to="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationAbstract_779a872e-575a-4e91-a772-11ecc806a5f8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationCashAndCashEquivalents_464771ef-5965-435c-b70c-eb46dd4b763d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationCashAndCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationAbstract_779a872e-575a-4e91-a772-11ecc806a5f8" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationCashAndCashEquivalents_464771ef-5965-435c-b70c-eb46dd4b763d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsNotesAndLoansReceivableNet_dee57b6c-29db-498f-b7c7-2fac9dda70a0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsNotesAndLoansReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationAbstract_779a872e-575a-4e91-a772-11ecc806a5f8" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsNotesAndLoansReceivableNet_dee57b6c-29db-498f-b7c7-2fac9dda70a0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationInventory1_ae62d8de-2a68-4ced-97c1-a47b508ecd66" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationInventory1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationAbstract_779a872e-575a-4e91-a772-11ecc806a5f8" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationInventory1_ae62d8de-2a68-4ced-97c1-a47b508ecd66" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationIntangibleAssets_943e5968-03b6-4238-b5cd-bc3643c69154" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationAbstract_779a872e-575a-4e91-a772-11ecc806a5f8" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationIntangibleAssets_943e5968-03b6-4238-b5cd-bc3643c69154" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherAssets_48da4767-78c7-4e6d-98e2-5e85a23952b8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationAbstract_779a872e-575a-4e91-a772-11ecc806a5f8" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherAssets_48da4767-78c7-4e6d-98e2-5e85a23952b8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_DisposalGroupIncludingDiscontinuedOperationAssetsGross_09b28a62-a61c-4fe2-9c96-70a215720b66" xlink:href="mygn-20240630.xsd#mygn_DisposalGroupIncludingDiscontinuedOperationAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationAbstract_779a872e-575a-4e91-a772-11ecc806a5f8" xlink:to="loc_mygn_DisposalGroupIncludingDiscontinuedOperationAssetsGross_09b28a62-a61c-4fe2-9c96-70a215720b66" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_DisposalGroupIncludingDiscontinuedOperationAssetsValuationAllowance_9352444e-fdeb-4bf1-bd9d-01b87bb47515" xlink:href="mygn-20240630.xsd#mygn_DisposalGroupIncludingDiscontinuedOperationAssetsValuationAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationAbstract_779a872e-575a-4e91-a772-11ecc806a5f8" xlink:to="loc_mygn_DisposalGroupIncludingDiscontinuedOperationAssetsValuationAllowance_9352444e-fdeb-4bf1-bd9d-01b87bb47515" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation_06886a52-52e2-4161-872f-acb8a8f533d4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationAbstract_779a872e-575a-4e91-a772-11ecc806a5f8" xlink:to="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation_06886a52-52e2-4161-872f-acb8a8f533d4" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationAbstract_e0a0f363-ca8f-4783-af80-5244ad11fa46" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_13688a4f-0c21-4dfb-a3d3-46926e6e5f5e" xlink:to="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationAbstract_e0a0f363-ca8f-4783-af80-5244ad11fa46" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherLiabilities_500b2ea4-8e16-4ff3-90b6-ec01d59fbd6b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationAbstract_e0a0f363-ca8f-4783-af80-5244ad11fa46" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherLiabilities_500b2ea4-8e16-4ff3-90b6-ec01d59fbd6b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation_3c73a334-1111-43a7-83a0-00f8b82bc018" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationAbstract_e0a0f363-ca8f-4783-af80-5244ad11fa46" xlink:to="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation_3c73a334-1111-43a7-83a0-00f8b82bc018" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_DisposalGroupIncludingDiscontinuedOperationNetAssets_80239cda-106b-44c3-af2e-7a983b8c9b03" xlink:href="mygn-20240630.xsd#mygn_DisposalGroupIncludingDiscontinuedOperationNetAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_13688a4f-0c21-4dfb-a3d3-46926e6e5f5e" xlink:to="loc_mygn_DisposalGroupIncludingDiscontinuedOperationNetAssets_80239cda-106b-44c3-af2e-7a983b8c9b03" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2024/ecd-2024.xsd#AwardTypeOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_OptionsAndRestrictedStockUnitsMember_665bcaa0-56d3-47a1-a4ef-6b8df3ccf174" xlink:href="mygn-20240630.xsd#mygn_OptionsAndRestrictedStockUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_mygn_OptionsAndRestrictedStockUnitsMember_665bcaa0-56d3-47a1-a4ef-6b8df3ccf174" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2024/ecd-2024.xsd#IndividualsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2024/ecd-2024.xsd#ecd_AllIndividualsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_RashmiKumarMember_d3dd8818-afab-4f05-9d69-834274ac467d" xlink:href="mygn-20240630.xsd#mygn_RashmiKumarMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_mygn_RashmiKumarMember_d3dd8818-afab-4f05-9d69-834274ac467d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_ColleenReitanMember_ea9c9f75-2e10-4c15-a307-da38fb5d5b1f" xlink:href="mygn-20240630.xsd#mygn_ColleenReitanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_mygn_ColleenReitanMember_ea9c9f75-2e10-4c15-a307-da38fb5d5b1f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_PaulDiazMember_12b7955c-1786-455d-bce6-f32ce14bde06" xlink:href="mygn-20240630.xsd#mygn_PaulDiazMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_mygn_PaulDiazMember_12b7955c-1786-455d-bce6-f32ce14bde06" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-roles-2024.xsd#eedm"/>
  <link:definitionLink xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_mygn_TestingMember_71db136f-d77d-487b-a463-6c869f3f169b" xlink:href="mygn-20240630.xsd#mygn_TestingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain" xlink:to="loc_mygn_TestingMember_71db136f-d77d-487b-a463-6c869f3f169b" xlink:type="arc" order="1"/>
  </link:definitionLink>
</link:linkbase>
