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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019ff673-f6b6-71ad-aac9-c8da56a4fbdd,g:d55b3226-436e-4715-b108-9f4840af0868-->
<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://indivior.com/role/CondensedConsolidatedStatementsofStockholdersDeficit" xlink:type="simple" xlink:href="indv-20260930.xsd#CondensedConsolidatedStatementsofStockholdersDeficit"/>
  <link:definitionLink xlink:role="http://indivior.com/role/CondensedConsolidatedStatementsofStockholdersDeficit" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019ff673-f747-794c-9168-857f4965c413" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019ff673-f747-77ec-a939-5e8a12704093" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019ff673-f747-794c-9168-857f4965c413" xlink:to="loc_us-gaap_StatementTable_019ff673-f747-77ec-a939-5e8a12704093" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019ff673-f747-75a6-aff8-1b5dc6f3f93e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019ff673-f747-77ec-a939-5e8a12704093" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019ff673-f747-75a6-aff8-1b5dc6f3f93e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019ff673-f747-75a6-aff8-1b5dc6f3f93e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019ff673-f747-75a6-aff8-1b5dc6f3f93e" xlink:to="loc_us-gaap_EquityComponentDomain_019ff673-f747-75a6-aff8-1b5dc6f3f93e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019ff673-f747-7fff-a0c1-1f18ed16e0ea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019ff673-f747-75a6-aff8-1b5dc6f3f93e" xlink:to="loc_us-gaap_EquityComponentDomain_019ff673-f747-7fff-a0c1-1f18ed16e0ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019ff673-f747-7536-a9e2-0b6c067553a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019ff673-f747-7fff-a0c1-1f18ed16e0ea" xlink:to="loc_us-gaap_CommonStockMember_019ff673-f747-7536-a9e2-0b6c067553a6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_019ff673-f747-7969-ae4e-25ff55893413" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019ff673-f747-7fff-a0c1-1f18ed16e0ea" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_019ff673-f747-7969-ae4e-25ff55893413" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_ShareRepurchaseCommitmentMember_019ff673-f747-7a13-befb-c677a18b50c5" xlink:href="indv-20260930.xsd#indv_ShareRepurchaseCommitmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019ff673-f747-7fff-a0c1-1f18ed16e0ea" xlink:to="loc_indv_ShareRepurchaseCommitmentMember_019ff673-f747-7a13-befb-c677a18b50c5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019ff673-f747-7969-94ab-132a9368683d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019ff673-f747-7fff-a0c1-1f18ed16e0ea" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019ff673-f747-7969-94ab-132a9368683d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019ff673-f747-7bf5-a1a2-b24e0efa3da5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019ff673-f747-7fff-a0c1-1f18ed16e0ea" xlink:to="loc_us-gaap_RetainedEarningsMember_019ff673-f747-7bf5-a1a2-b24e0efa3da5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ff673-f747-7ee4-a2ae-d399e42a1493" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019ff673-f747-794c-9168-857f4965c413" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ff673-f747-7ee4-a2ae-d399e42a1493" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_019ff673-f747-7299-8a15-710246570cf7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ff673-f747-7ee4-a2ae-d399e42a1493" xlink:to="loc_us-gaap_CommonStockSharesIssued_019ff673-f747-7299-8a15-710246570cf7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019ff673-f747-737f-8f5b-41043d9802a1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ff673-f747-7ee4-a2ae-d399e42a1493" xlink:to="loc_us-gaap_StockholdersEquity_019ff673-f747-737f-8f5b-41043d9802a1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_StockCanceledAndExchangedDueToRedomicileValue_019ff673-f747-786c-950e-9138692f3c43" xlink:href="indv-20260930.xsd#indv_StockCanceledAndExchangedDueToRedomicileValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ff673-f747-7ee4-a2ae-d399e42a1493" xlink:to="loc_indv_StockCanceledAndExchangedDueToRedomicileValue_019ff673-f747-786c-950e-9138692f3c43" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019ff673-f747-7e5a-83ab-61c5ef8b3516" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ff673-f747-7ee4-a2ae-d399e42a1493" xlink:to="loc_us-gaap_NetIncomeLoss_019ff673-f747-7e5a-83ab-61c5ef8b3516" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019ff673-f747-7df2-be0d-f7551f7bd011" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ff673-f747-7ee4-a2ae-d399e42a1493" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019ff673-f747-7df2-be0d-f7551f7bd011" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019ff673-f747-7beb-a048-06a3f35d3efa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ff673-f747-7ee4-a2ae-d399e42a1493" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019ff673-f747-7beb-a048-06a3f35d3efa" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_019ff673-f747-7130-941a-c1a2caa7c030" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ff673-f747-7ee4-a2ae-d399e42a1493" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_019ff673-f747-7130-941a-c1a2caa7c030" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_019ff673-f747-7252-b9b6-2b426be77ce9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ff673-f747-7ee4-a2ae-d399e42a1493" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_019ff673-f747-7252-b9b6-2b426be77ce9" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_019ff673-f747-7ab2-b0ac-a4bc95510f01" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ff673-f747-7ee4-a2ae-d399e42a1493" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_019ff673-f747-7ab2-b0ac-a4bc95510f01" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019ff673-f747-72a5-ab99-2b8f0ffc8bdd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ff673-f747-7ee4-a2ae-d399e42a1493" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019ff673-f747-72a5-ab99-2b8f0ffc8bdd" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_ShareRepurchaseLiabilityIncreaseDecreaseInEquity_019ff673-f747-7b83-838d-45f2f9759b17" xlink:href="indv-20260930.xsd#indv_ShareRepurchaseLiabilityIncreaseDecreaseInEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ff673-f747-7ee4-a2ae-d399e42a1493" xlink:to="loc_indv_ShareRepurchaseLiabilityIncreaseDecreaseInEquity_019ff673-f747-7b83-838d-45f2f9759b17" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_019ff673-f747-7b85-8799-246fbe6ccddc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ff673-f747-7ee4-a2ae-d399e42a1493" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_019ff673-f747-7b85-8799-246fbe6ccddc" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityOther_019ff673-f747-7536-93c8-2dba7a758cec" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019ff673-f747-7ee4-a2ae-d399e42a1493" xlink:to="loc_us-gaap_StockholdersEquityOther_019ff673-f747-7536-93c8-2dba7a758cec" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_019ff673-f747-7a6b-a7be-1d020b73f3a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019ff673-f747-7286-9131-673ecdf89532" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://indivior.com/role/BusinessOverviewBasisofPresentationandRecentlyIssuedAccountingStandardsDetails" xlink:type="simple" xlink:href="indv-20260930.xsd#BusinessOverviewBasisofPresentationandRecentlyIssuedAccountingStandardsDetails"/>
  <link:definitionLink xlink:role="http://indivior.com/role/BusinessOverviewBasisofPresentationandRecentlyIssuedAccountingStandardsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_01a10ca5-ca7b-76e9-bde4-52e13fddba35" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_01a10ca5-ca7b-7ac4-bba9-e34d3e311548" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a10ca5-ca7b-76e9-bde4-52e13fddba35" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_01a10ca5-ca7b-7ac4-bba9-e34d3e311548" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_01a10ca5-ca7b-758b-9837-92c5d9d6f0ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_01a10ca5-ca7b-7ac4-bba9-e34d3e311548" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_01a10ca5-ca7b-758b-9837-92c5d9d6f0ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_01a10ca5-ca7b-758b-9837-92c5d9d6f0ef_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_01a10ca5-ca7b-758b-9837-92c5d9d6f0ef" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_01a10ca5-ca7b-758b-9837-92c5d9d6f0ef_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_01a10ca5-ca7b-73c2-ac7b-515e04bc82be" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_01a10ca5-ca7b-758b-9837-92c5d9d6f0ef" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_01a10ca5-ca7b-73c2-ac7b-515e04bc82be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_SupernusPharmaceuticalsInc.Member_01a10ca5-ca7b-77cf-9b03-1995e0703117" xlink:href="indv-20260930.xsd#indv_SupernusPharmaceuticalsInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_01a10ca5-ca7b-73c2-ac7b-515e04bc82be" xlink:to="loc_indv_SupernusPharmaceuticalsInc.Member_01a10ca5-ca7b-77cf-9b03-1995e0703117" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_01a10ca5-ca7b-74be-8d2d-069df6601956" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_01a10ca5-ca7b-7ac4-bba9-e34d3e311548" xlink:to="loc_dei_LegalEntityAxis_01a10ca5-ca7b-74be-8d2d-069df6601956" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_01a10ca5-ca7b-74be-8d2d-069df6601956_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_01a10ca5-ca7b-74be-8d2d-069df6601956" xlink:to="loc_dei_EntityDomain_01a10ca5-ca7b-74be-8d2d-069df6601956_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_01a10ca5-ca7b-78fa-85db-859e831678f7" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_01a10ca5-ca7b-74be-8d2d-069df6601956" xlink:to="loc_dei_EntityDomain_01a10ca5-ca7b-78fa-85db-859e831678f7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_SupernusPharmaceuticalsInc.Member_01a179be-f416-7973-b3c1-91efff2cac42" xlink:href="indv-20260930.xsd#indv_SupernusPharmaceuticalsInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_01a10ca5-ca7b-78fa-85db-859e831678f7" xlink:to="loc_indv_SupernusPharmaceuticalsInc.Member_01a179be-f416-7973-b3c1-91efff2cac42" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_IndiviorStockholdersMember_01a10ca5-ca7b-70dc-8674-7eac65217d5a" xlink:href="indv-20260930.xsd#indv_IndiviorStockholdersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_01a10ca5-ca7b-78fa-85db-859e831678f7" xlink:to="loc_indv_IndiviorStockholdersMember_01a10ca5-ca7b-70dc-8674-7eac65217d5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_SupernusStockholdersMember_01a10ca5-ca7b-7f3b-a730-9127c5e70fdd" xlink:href="indv-20260930.xsd#indv_SupernusStockholdersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_01a10ca5-ca7b-78fa-85db-859e831678f7" xlink:to="loc_indv_SupernusStockholdersMember_01a10ca5-ca7b-7f3b-a730-9127c5e70fdd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_01a10ca5-ca7b-76f1-9afe-0ae8ea742685" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_01a10ca5-ca7b-7ac4-bba9-e34d3e311548" xlink:to="loc_srt_StatementScenarioAxis_01a10ca5-ca7b-76f1-9afe-0ae8ea742685" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_01a10ca5-ca7b-76f1-9afe-0ae8ea742685_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_01a10ca5-ca7b-76f1-9afe-0ae8ea742685" xlink:to="loc_srt_ScenarioUnspecifiedDomain_01a10ca5-ca7b-76f1-9afe-0ae8ea742685_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_01a10ca5-ca7b-7719-a216-0d50d6c37060" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_01a10ca5-ca7b-76f1-9afe-0ae8ea742685" xlink:to="loc_srt_ScenarioUnspecifiedDomain_01a10ca5-ca7b-7719-a216-0d50d6c37060" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_01a10ca5-ca7b-79a3-afef-aa0bbb6ebb7b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_01a10ca5-ca7b-7719-a216-0d50d6c37060" xlink:to="loc_srt_ScenarioForecastMember_01a10ca5-ca7b-79a3-afef-aa0bbb6ebb7b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_01a10ca5-ca7b-742c-8b3c-a23f22c74b82" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_01a10ca5-ca7b-7ac4-bba9-e34d3e311548" xlink:to="loc_us-gaap_DebtInstrumentAxis_01a10ca5-ca7b-742c-8b3c-a23f22c74b82" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_01a10ca5-ca7b-742c-8b3c-a23f22c74b82_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_01a10ca5-ca7b-742c-8b3c-a23f22c74b82" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_01a10ca5-ca7b-742c-8b3c-a23f22c74b82_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_01a10ca5-ca7b-760a-a361-faab6c541a5a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_01a10ca5-ca7b-742c-8b3c-a23f22c74b82" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_01a10ca5-ca7b-760a-a361-faab6c541a5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_AcquisitionTermLoanMember_01a10ca5-ca7b-79f2-9ee7-c75a87c4f87f" xlink:href="indv-20260930.xsd#indv_AcquisitionTermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_01a10ca5-ca7b-760a-a361-faab6c541a5a" xlink:to="loc_indv_AcquisitionTermLoanMember_01a10ca5-ca7b-79f2-9ee7-c75a87c4f87f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_01a10ca5-ca7b-7890-86f1-e78ca5b358f4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_01a10ca5-ca7b-7ac4-bba9-e34d3e311548" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_01a10ca5-ca7b-7890-86f1-e78ca5b358f4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_01a10ca5-ca7b-7890-86f1-e78ca5b358f4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_01a10ca5-ca7b-7890-86f1-e78ca5b358f4" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_01a10ca5-ca7b-7890-86f1-e78ca5b358f4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_01a10ca5-ca7b-7796-8370-8e8dbf274d0b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_01a10ca5-ca7b-7890-86f1-e78ca5b358f4" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_01a10ca5-ca7b-7796-8370-8e8dbf274d0b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_01a10ca5-ca7b-77f3-b39f-19fa97fa60f7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_01a10ca5-ca7b-7796-8370-8e8dbf274d0b" xlink:to="loc_us-gaap_UnsecuredDebtMember_01a10ca5-ca7b-77f3-b39f-19fa97fa60f7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_01a13ddb-1965-7b36-a731-3d28406fcebf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_01a10ca5-ca7b-7ac4-bba9-e34d3e311548" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_01a13ddb-1965-7b36-a731-3d28406fcebf" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_01a13ddb-1965-7b36-a731-3d28406fcebf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_01a13ddb-1965-7b36-a731-3d28406fcebf" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_01a13ddb-1965-7b36-a731-3d28406fcebf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_01a13ddb-1965-727b-ab39-cc87e1fd3745" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_01a13ddb-1965-7b36-a731-3d28406fcebf" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_01a13ddb-1965-727b-ab39-cc87e1fd3745" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_01a13ddb-1965-7034-ac5f-95e015329229" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_01a13ddb-1965-727b-ab39-cc87e1fd3745" xlink:to="loc_us-gaap_SubsequentEventMember_01a13ddb-1965-7034-ac5f-95e015329229" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_BusinessCombinationShareExchangeRatio_01a10ca5-ca7b-7cb0-a5c5-ddb74e2abd35" xlink:href="indv-20260930.xsd#indv_BusinessCombinationShareExchangeRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a10ca5-ca7b-76e9-bde4-52e13fddba35" xlink:to="loc_indv_BusinessCombinationShareExchangeRatio_01a10ca5-ca7b-7cb0-a5c5-ddb74e2abd35" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_BusinessCombinationFeeUponTerminationOfAgreement_01a179be-2a10-7292-b2ea-d265cb0152a9" xlink:href="indv-20260930.xsd#indv_BusinessCombinationFeeUponTerminationOfAgreement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a10ca5-ca7b-76e9-bde4-52e13fddba35" xlink:to="loc_indv_BusinessCombinationFeeUponTerminationOfAgreement_01a179be-2a10-7292-b2ea-d265cb0152a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_StockholdersOwnershipPercentage_01a10ca5-ca7b-798b-af79-ecee68b82899" xlink:href="indv-20260930.xsd#indv_StockholdersOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a10ca5-ca7b-76e9-bde4-52e13fddba35" xlink:to="loc_indv_StockholdersOwnershipPercentage_01a10ca5-ca7b-798b-af79-ecee68b82899" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStockCash_01a10ca5-ca7b-7b00-9895-2f0383e5f6cd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DividendsCommonStockCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a10ca5-ca7b-76e9-bde4-52e13fddba35" xlink:to="loc_us-gaap_DividendsCommonStockCash_01a10ca5-ca7b-7b00-9895-2f0383e5f6cd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_CommitmentsToExtendCredit_01a10ca5-ca7b-73e6-8a10-e7784e2e512a" xlink:href="indv-20260930.xsd#indv_CommitmentsToExtendCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a10ca5-ca7b-76e9-bde4-52e13fddba35" xlink:to="loc_indv_CommitmentsToExtendCredit_01a10ca5-ca7b-73e6-8a10-e7784e2e512a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_NumberOfIndividualsOnBoardOfDirectors_01a179c2-fe17-7ff6-9dd5-d3f3f859758e" xlink:href="indv-20260930.xsd#indv_NumberOfIndividualsOnBoardOfDirectors"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a10ca5-ca7b-76e9-bde4-52e13fddba35" xlink:to="loc_indv_NumberOfIndividualsOnBoardOfDirectors_01a179c2-fe17-7ff6-9dd5-d3f3f859758e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_NumberOfIndividualsOnBoardOfDirectorsNominatedByEachCompany_01a179c2-fe17-7246-bfd3-3fff09f448f1" xlink:href="indv-20260930.xsd#indv_NumberOfIndividualsOnBoardOfDirectorsNominatedByEachCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a10ca5-ca7b-76e9-bde4-52e13fddba35" xlink:to="loc_indv_NumberOfIndividualsOnBoardOfDirectorsNominatedByEachCompany_01a179c2-fe17-7246-bfd3-3fff09f448f1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_01a13ddb-1965-73c8-8a04-1a413b14ead7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_01a10ca5-ca7b-76e9-bde4-52e13fddba35" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_01a13ddb-1965-73c8-8a04-1a413b14ead7" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://indivior.com/role/SegmentGeographicandOtherRevenueInformationFinancialDataProvidedtotheCODMDetails" xlink:type="simple" xlink:href="indv-20260930.xsd#SegmentGeographicandOtherRevenueInformationFinancialDataProvidedtotheCODMDetails"/>
  <link:definitionLink xlink:role="http://indivior.com/role/SegmentGeographicandOtherRevenueInformationFinancialDataProvidedtotheCODMDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019ff673-f747-76d5-8f18-f10c58814943" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019ff673-f747-76bb-817f-4c1f0399b176" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ff673-f747-76d5-8f18-f10c58814943" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019ff673-f747-76bb-817f-4c1f0399b176" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019ff673-f747-73b8-9492-202a6653bbe7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019ff673-f747-76bb-817f-4c1f0399b176" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019ff673-f747-73b8-9492-202a6653bbe7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019ff673-f747-73b8-9492-202a6653bbe7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019ff673-f747-73b8-9492-202a6653bbe7" xlink:to="loc_us-gaap_SegmentDomain_019ff673-f747-73b8-9492-202a6653bbe7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019ff673-f747-7d38-8b17-ab4d88a1a154" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019ff673-f747-73b8-9492-202a6653bbe7" xlink:to="loc_us-gaap_SegmentDomain_019ff673-f747-7d38-8b17-ab4d88a1a154" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_ReportableSegmentMember_019ff673-f747-7444-83de-8316029cac94" xlink:href="indv-20260930.xsd#indv_ReportableSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019ff673-f747-7d38-8b17-ab4d88a1a154" xlink:to="loc_indv_ReportableSegmentMember_019ff673-f747-7444-83de-8316029cac94" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019ff673-f747-7f92-ad90-8cbf687d24ba" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019ff673-f747-76bb-817f-4c1f0399b176" xlink:to="loc_srt_StatementGeographicalAxis_019ff673-f747-7f92-ad90-8cbf687d24ba" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019ff673-f747-7f92-ad90-8cbf687d24ba_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019ff673-f747-7f92-ad90-8cbf687d24ba" xlink:to="loc_srt_SegmentGeographicalDomain_019ff673-f747-7f92-ad90-8cbf687d24ba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019ff673-f747-71e7-a9ef-339798c2fa49" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019ff673-f747-7f92-ad90-8cbf687d24ba" xlink:to="loc_srt_SegmentGeographicalDomain_019ff673-f747-71e7-a9ef-339798c2fa49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019ff673-f747-785a-9335-708668562121" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019ff673-f747-71e7-a9ef-339798c2fa49" xlink:to="loc_country_US_019ff673-f747-785a-9335-708668562121" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_019ff673-f747-73d2-a27d-2f514115b2d6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019ff673-f747-71e7-a9ef-339798c2fa49" xlink:to="loc_us-gaap_NonUsMember_019ff673-f747-73d2-a27d-2f514115b2d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019ff673-f747-7f05-bf0d-7fadc04f0190" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019ff673-f747-76bb-817f-4c1f0399b176" xlink:to="loc_srt_ProductOrServiceAxis_019ff673-f747-7f05-bf0d-7fadc04f0190" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019ff673-f747-7f05-bf0d-7fadc04f0190_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019ff673-f747-7f05-bf0d-7fadc04f0190" xlink:to="loc_srt_ProductsAndServicesDomain_019ff673-f747-7f05-bf0d-7fadc04f0190_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019ff673-f747-7790-9977-14c9c008514f" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019ff673-f747-7f05-bf0d-7fadc04f0190" xlink:to="loc_srt_ProductsAndServicesDomain_019ff673-f747-7790-9977-14c9c008514f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_SublocadeMember_019ff673-f747-705d-9481-f02da31d3937" xlink:href="indv-20260930.xsd#indv_SublocadeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019ff673-f747-7790-9977-14c9c008514f" xlink:to="loc_indv_SublocadeMember_019ff673-f747-705d-9481-f02da31d3937" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_SublingualAndOtherMember_019ff673-f747-7d0a-a8c9-80fd47976cae" xlink:href="indv-20260930.xsd#indv_SublingualAndOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019ff673-f747-7790-9977-14c9c008514f" xlink:to="loc_indv_SublingualAndOtherMember_019ff673-f747-7d0a-a8c9-80fd47976cae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_OPVEEMember_01a0485a-6d5f-7fe6-86d3-6b6cddc5969c" xlink:href="indv-20260930.xsd#indv_OPVEEMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019ff673-f747-7790-9977-14c9c008514f" xlink:to="loc_indv_OPVEEMember_01a0485a-6d5f-7fe6-86d3-6b6cddc5969c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_PerserisMember_019ff673-f747-7dd1-8562-e76bf6a6cad9" xlink:href="indv-20260930.xsd#indv_PerserisMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019ff673-f747-7790-9977-14c9c008514f" xlink:to="loc_indv_PerserisMember_019ff673-f747-7dd1-8562-e76bf6a6cad9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019ff673-f747-7285-870f-b1c2775e95d2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ff673-f747-76d5-8f18-f10c58814943" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019ff673-f747-7285-870f-b1c2775e95d2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_019ff673-f747-7670-b8f8-26eaa4965107" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ff673-f747-76d5-8f18-f10c58814943" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_019ff673-f747-7670-b8f8-26eaa4965107" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_019ff673-f747-7758-b924-a8b7d10a2c0e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ff673-f747-76d5-8f18-f10c58814943" xlink:to="loc_us-gaap_GrossProfit_019ff673-f747-7758-b924-a8b7d10a2c0e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract_019ff673-f747-7f66-bd67-e82678f4018c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ff673-f747-76d5-8f18-f10c58814943" xlink:to="loc_us-gaap_OperatingExpensesAbstract_019ff673-f747-7f66-bd67-e82678f4018c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019ff673-f747-705c-a90b-d52251d230b8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019ff673-f747-7f66-bd67-e82678f4018c" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019ff673-f747-705c-a90b-d52251d230b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost_019ff673-f747-7351-a4ca-55df95ac4bdf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019ff673-f747-7f66-bd67-e82678f4018c" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost_019ff673-f747-7351-a4ca-55df95ac4bdf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_019ff673-f747-7f14-908d-bd98110a07d6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019ff673-f747-7f66-bd67-e82678f4018c" xlink:to="loc_us-gaap_OperatingExpenses_019ff673-f747-7f14-908d-bd98110a07d6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInterest_019ff673-f747-7c8a-88df-e97a6a8d4692" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentIncomeInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ff673-f747-76d5-8f18-f10c58814943" xlink:to="loc_us-gaap_InvestmentIncomeInterest_019ff673-f747-7c8a-88df-e97a6a8d4692" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseNonoperating_019ff673-f747-7340-97b5-7ff9aed90f95" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpenseNonoperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ff673-f747-76d5-8f18-f10c58814943" xlink:to="loc_us-gaap_InterestExpenseNonoperating_019ff673-f747-7340-97b5-7ff9aed90f95" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019ff673-f747-78aa-b058-78a8fc0d3d9b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ff673-f747-76d5-8f18-f10c58814943" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019ff673-f747-78aa-b058-78a8fc0d3d9b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019ff673-f747-7ff9-86c3-31cd80d089b5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ff673-f747-76d5-8f18-f10c58814943" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019ff673-f747-7ff9-86c3-31cd80d089b5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019ff673-f747-7cdb-96ba-d184a403ae88" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ff673-f747-76d5-8f18-f10c58814943" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019ff673-f747-7cdb-96ba-d184a403ae88" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019ff673-f747-7ded-8a1b-c56dfa322649" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ff673-f747-76d5-8f18-f10c58814943" xlink:to="loc_us-gaap_NetIncomeLoss_019ff673-f747-7ded-8a1b-c56dfa322649" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_019ff673-f747-7b1e-aafd-272ba3aa4cd1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ff673-f747-76d5-8f18-f10c58814943" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_019ff673-f747-7b1e-aafd-272ba3aa4cd1" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_019ff673-f747-7339-a5fc-61e3adcb6ebd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019ff673-f747-76d5-8f18-f10c58814943" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_019ff673-f747-7339-a5fc-61e3adcb6ebd" xlink:type="arc" order="11"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://indivior.com/role/PropertyPlantandEquipmentNetSummaryofPropertyPlantandEquipmentNetDetails" xlink:type="simple" xlink:href="indv-20260930.xsd#PropertyPlantandEquipmentNetSummaryofPropertyPlantandEquipmentNetDetails"/>
  <link:definitionLink xlink:role="http://indivior.com/role/PropertyPlantandEquipmentNetSummaryofPropertyPlantandEquipmentNetDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ff673-f747-7870-8edd-cf9cd6f24eab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019ff673-f747-78db-96d3-44d6883a28de" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ff673-f747-7870-8edd-cf9cd6f24eab" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019ff673-f747-78db-96d3-44d6883a28de" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019ff673-f747-7ab0-9808-ed838ca202bd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019ff673-f747-78db-96d3-44d6883a28de" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019ff673-f747-7ab0-9808-ed838ca202bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ff673-f747-7ab0-9808-ed838ca202bd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019ff673-f747-7ab0-9808-ed838ca202bd" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ff673-f747-7ab0-9808-ed838ca202bd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ff673-f747-7a7e-b3d0-16ba3e566192" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019ff673-f747-7ab0-9808-ed838ca202bd" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ff673-f747-7a7e-b3d0-16ba3e566192" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandAndBuildingMember_019ff673-f747-74fb-b694-a1454f3cc140" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LandAndBuildingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ff673-f747-7a7e-b3d0-16ba3e566192" xlink:to="loc_us-gaap_LandAndBuildingMember_019ff673-f747-74fb-b694-a1454f3cc140" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_PlantAndEquipmentMember_019ff673-f747-7086-8ac5-4d8ad078dba3" xlink:href="indv-20260930.xsd#indv_PlantAndEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ff673-f747-7a7e-b3d0-16ba3e566192" xlink:to="loc_indv_PlantAndEquipmentMember_019ff673-f747-7086-8ac5-4d8ad078dba3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressMember_019ff673-f747-7a8c-b5e6-0a51684cd10b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConstructionInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019ff673-f747-7a7e-b3d0-16ba3e566192" xlink:to="loc_us-gaap_ConstructionInProgressMember_019ff673-f747-7a8c-b5e6-0a51684cd10b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_019ff673-f747-72f2-a076-3fc8b5c02e37" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ff673-f747-7870-8edd-cf9cd6f24eab" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_019ff673-f747-72f2-a076-3fc8b5c02e37" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_019ff673-f747-73e6-b1aa-98ca4dcbde8d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ff673-f747-7870-8edd-cf9cd6f24eab" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_019ff673-f747-73e6-b1aa-98ca4dcbde8d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_019ff673-f747-74de-a03e-a1f2f9a5f56b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019ff673-f747-7870-8edd-cf9cd6f24eab" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_019ff673-f747-74de-a03e-a1f2f9a5f56b" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://indivior.com/role/AccruedLitigationSettlementExpensesSummaryDetails" xlink:type="simple" xlink:href="indv-20260930.xsd#AccruedLitigationSettlementExpensesSummaryDetails"/>
  <link:definitionLink xlink:role="http://indivior.com/role/AccruedLitigationSettlementExpensesSummaryDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_019ff673-f747-74ca-8c08-9656cac5ca73" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_019ff673-f747-7bfa-8a6b-a753f0b55767" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_019ff673-f747-74ca-8c08-9656cac5ca73" xlink:to="loc_us-gaap_LossContingenciesTable_019ff673-f747-7bfa-8a6b-a753f0b55767" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_019ff673-f747-79af-958c-eb29448054b5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019ff673-f747-7bfa-8a6b-a753f0b55767" xlink:to="loc_srt_LitigationCaseAxis_019ff673-f747-79af-958c-eb29448054b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_019ff673-f747-79af-958c-eb29448054b5_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_019ff673-f747-79af-958c-eb29448054b5" xlink:to="loc_srt_LitigationCaseTypeDomain_019ff673-f747-79af-958c-eb29448054b5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_019ff673-f747-7ede-bfd2-4d977fa5898a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_019ff673-f747-79af-958c-eb29448054b5" xlink:to="loc_srt_LitigationCaseTypeDomain_019ff673-f747-7ede-bfd2-4d977fa5898a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_OpioidLitigationMember_019ff673-f747-7d1a-b72d-cc470942f6f5" xlink:href="indv-20260930.xsd#indv_OpioidLitigationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019ff673-f747-7ede-bfd2-4d977fa5898a" xlink:to="loc_indv_OpioidLitigationMember_019ff673-f747-7d1a-b72d-cc470942f6f5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_OtherLitigationMember_019ff673-f747-7212-b1a1-679845fd057f" xlink:href="indv-20260930.xsd#indv_OtherLitigationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019ff673-f747-7ede-bfd2-4d977fa5898a" xlink:to="loc_indv_OtherLitigationMember_019ff673-f747-7212-b1a1-679845fd057f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationReserveCurrent_019ff673-f747-7fb4-8cf5-e339047e56a3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LitigationReserveCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019ff673-f747-74ca-8c08-9656cac5ca73" xlink:to="loc_us-gaap_LitigationReserveCurrent_019ff673-f747-7fb4-8cf5-e339047e56a3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationReserveNoncurrent_019ff673-f747-7d14-baf1-2e0de95899ce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LitigationReserveNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019ff673-f747-74ca-8c08-9656cac5ca73" xlink:to="loc_us-gaap_LitigationReserveNoncurrent_019ff673-f747-7d14-baf1-2e0de95899ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationReserve_019ff673-f747-7136-9c53-83871f55bc9f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LitigationReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019ff673-f747-74ca-8c08-9656cac5ca73" xlink:to="loc_us-gaap_LitigationReserve_019ff673-f747-7136-9c53-83871f55bc9f" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://indivior.com/role/AccruedLitigationSettlementExpensesNarrativeDetails" xlink:type="simple" xlink:href="indv-20260930.xsd#AccruedLitigationSettlementExpensesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://indivior.com/role/AccruedLitigationSettlementExpensesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_019ff673-f747-7a06-ba5c-ee41fc21d72e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_019ff673-f747-7b22-9382-d695fd187946" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_019ff673-f747-7a06-ba5c-ee41fc21d72e" xlink:to="loc_us-gaap_LossContingenciesTable_019ff673-f747-7b22-9382-d695fd187946" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_019ff673-f747-74dd-ad78-f192c8b643a9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019ff673-f747-7b22-9382-d695fd187946" xlink:to="loc_srt_LitigationCaseAxis_019ff673-f747-74dd-ad78-f192c8b643a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_019ff673-f747-74dd-ad78-f192c8b643a9_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_019ff673-f747-74dd-ad78-f192c8b643a9" xlink:to="loc_srt_LitigationCaseTypeDomain_019ff673-f747-74dd-ad78-f192c8b643a9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_019ff673-f747-7145-a340-9bf748244ee3" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_019ff673-f747-74dd-ad78-f192c8b643a9" xlink:to="loc_srt_LitigationCaseTypeDomain_019ff673-f747-7145-a340-9bf748244ee3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_OpioidLitigationMember_019ff673-f747-707a-8752-6a0148c648ec" xlink:href="indv-20260930.xsd#indv_OpioidLitigationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019ff673-f747-7145-a340-9bf748244ee3" xlink:to="loc_indv_OpioidLitigationMember_019ff673-f747-707a-8752-6a0148c648ec" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_IndemnitySettlementMember_019ff673-f747-747f-b8e2-3aa5dfb3c5a3" xlink:href="indv-20260930.xsd#indv_IndemnitySettlementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019ff673-f747-7145-a340-9bf748244ee3" xlink:to="loc_indv_IndemnitySettlementMember_019ff673-f747-747f-b8e2-3aa5dfb3c5a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationReserve_019ff673-f747-7d70-b6c1-8a134a1d0460" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LitigationReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019ff673-f747-7a06-ba5c-ee41fc21d72e" xlink:to="loc_us-gaap_LitigationReserve_019ff673-f747-7d70-b6c1-8a134a1d0460" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForLegalSettlements_019ff673-f747-7a3e-b4c1-d60ddd22ab24" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForLegalSettlements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019ff673-f747-7a06-ba5c-ee41fc21d72e" xlink:to="loc_us-gaap_PaymentsForLegalSettlements_019ff673-f747-7a3e-b4c1-d60ddd22ab24" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://indivior.com/role/DebtDetails" xlink:type="simple" xlink:href="indv-20260930.xsd#DebtDetails"/>
  <link:definitionLink xlink:role="http://indivior.com/role/DebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019ff673-f747-7f60-8194-db175d28fa77" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_us-gaap_DebtInstrumentTable_019ff673-f747-7f60-8194-db175d28fa77" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019ff673-f747-7787-b082-94de211ae812" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019ff673-f747-7f60-8194-db175d28fa77" xlink:to="loc_us-gaap_DebtInstrumentAxis_019ff673-f747-7787-b082-94de211ae812" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019ff673-f747-7787-b082-94de211ae812_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019ff673-f747-7787-b082-94de211ae812" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019ff673-f747-7787-b082-94de211ae812_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019ff673-f747-7a95-a7c1-987273ca4e5c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019ff673-f747-7787-b082-94de211ae812" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019ff673-f747-7a95-a7c1-987273ca4e5c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_ConvertibleSeniorNotesDue2031Member_019ff673-f747-76a3-a22c-0b8f0db23e9a" xlink:href="indv-20260930.xsd#indv_ConvertibleSeniorNotesDue2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019ff673-f747-7a95-a7c1-987273ca4e5c" xlink:to="loc_indv_ConvertibleSeniorNotesDue2031Member_019ff673-f747-76a3-a22c-0b8f0db23e9a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_ConvertibleSeniorNotesDue2031OverAllotmentOptionMember_019ff673-f747-73df-9e98-ca4d0730ea8c" xlink:href="indv-20260930.xsd#indv_ConvertibleSeniorNotesDue2031OverAllotmentOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019ff673-f747-7a95-a7c1-987273ca4e5c" xlink:to="loc_indv_ConvertibleSeniorNotesDue2031OverAllotmentOptionMember_019ff673-f747-73df-9e98-ca4d0730ea8c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_NotePurchaseAgreementMember_019ff673-f747-726d-8a86-52cc1bb1e968" xlink:href="indv-20260930.xsd#indv_NotePurchaseAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019ff673-f747-7a95-a7c1-987273ca4e5c" xlink:to="loc_indv_NotePurchaseAgreementMember_019ff673-f747-726d-8a86-52cc1bb1e968" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019ff673-f747-7f9c-beb4-7b7c010ba355" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019ff673-f747-7f60-8194-db175d28fa77" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019ff673-f747-7f9c-beb4-7b7c010ba355" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019ff673-f747-7f9c-beb4-7b7c010ba355_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019ff673-f747-7f9c-beb4-7b7c010ba355" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019ff673-f747-7f9c-beb4-7b7c010ba355_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019ff673-f747-77e1-92f1-3bc973160e4a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019ff673-f747-7f9c-beb4-7b7c010ba355" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019ff673-f747-77e1-92f1-3bc973160e4a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_019ff673-f747-779b-83bc-8c94f59f9d2e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019ff673-f747-77e1-92f1-3bc973160e4a" xlink:to="loc_us-gaap_ConvertibleDebtMember_019ff673-f747-779b-83bc-8c94f59f9d2e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_019ff673-f747-7fe9-a049-2b267c02bf8b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019ff673-f747-77e1-92f1-3bc973160e4a" xlink:to="loc_us-gaap_SecuredDebtMember_019ff673-f747-7fe9-a049-2b267c02bf8b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_DebtInstrumentConvertibleTermsOfConversionAxis_019ff673-f747-7472-b28e-90fb570ad40e" xlink:href="indv-20260930.xsd#indv_DebtInstrumentConvertibleTermsOfConversionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019ff673-f747-7f60-8194-db175d28fa77" xlink:to="loc_indv_DebtInstrumentConvertibleTermsOfConversionAxis_019ff673-f747-7472-b28e-90fb570ad40e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_DebtInstrumentConvertibleTermsOfConversionDomain_019ff673-f747-7472-b28e-90fb570ad40e_default" xlink:href="indv-20260930.xsd#indv_DebtInstrumentConvertibleTermsOfConversionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_indv_DebtInstrumentConvertibleTermsOfConversionAxis_019ff673-f747-7472-b28e-90fb570ad40e" xlink:to="loc_indv_DebtInstrumentConvertibleTermsOfConversionDomain_019ff673-f747-7472-b28e-90fb570ad40e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_DebtInstrumentConvertibleTermsOfConversionDomain_019ff673-f747-7799-80a6-ec5fea084904" xlink:href="indv-20260930.xsd#indv_DebtInstrumentConvertibleTermsOfConversionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_indv_DebtInstrumentConvertibleTermsOfConversionAxis_019ff673-f747-7472-b28e-90fb570ad40e" xlink:to="loc_indv_DebtInstrumentConvertibleTermsOfConversionDomain_019ff673-f747-7799-80a6-ec5fea084904" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_DebtConversionTermsOneMember_019ff673-f747-7467-9c59-7242d4f57195" xlink:href="indv-20260930.xsd#indv_DebtConversionTermsOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_indv_DebtInstrumentConvertibleTermsOfConversionDomain_019ff673-f747-7799-80a6-ec5fea084904" xlink:to="loc_indv_DebtConversionTermsOneMember_019ff673-f747-7467-9c59-7242d4f57195" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_DebtConversionTermsTwoMember_019ff673-f747-706e-b415-bc476854daa8" xlink:href="indv-20260930.xsd#indv_DebtConversionTermsTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_indv_DebtInstrumentConvertibleTermsOfConversionDomain_019ff673-f747-7799-80a6-ec5fea084904" xlink:to="loc_indv_DebtConversionTermsTwoMember_019ff673-f747-706e-b415-bc476854daa8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019ff673-f747-7799-8223-02465e75ece9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019ff673-f747-7f60-8194-db175d28fa77" xlink:to="loc_srt_RangeAxis_019ff673-f747-7799-8223-02465e75ece9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ff673-f747-7799-8223-02465e75ece9_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019ff673-f747-7799-8223-02465e75ece9" xlink:to="loc_srt_RangeMember_019ff673-f747-7799-8223-02465e75ece9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ff673-f747-7e96-a6bb-fc26acb69ed5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019ff673-f747-7799-8223-02465e75ece9" xlink:to="loc_srt_RangeMember_019ff673-f747-7e96-a6bb-fc26acb69ed5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019ff673-f747-7f72-a4ca-4155c3010f4a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ff673-f747-7e96-a6bb-fc26acb69ed5" xlink:to="loc_srt_MaximumMember_019ff673-f747-7f72-a4ca-4155c3010f4a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_019ff673-f747-7fe6-bc1e-8caf19b9d576" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_019ff673-f747-7fe6-bc1e-8caf19b9d576" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019ff673-f747-7a1d-85a6-bcc8930810ba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019ff673-f747-7a1d-85a6-bcc8930810ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromConvertibleDebt_019ff673-f747-7e96-9eff-21aa7f3711c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromConvertibleDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_us-gaap_ProceedsFromConvertibleDebt_019ff673-f747-7e96-9eff-21aa7f3711c2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsGross_019ff673-f747-78b1-97b1-bf1e6eb9e776" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredFinanceCostsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_us-gaap_DeferredFinanceCostsGross_019ff673-f747-78b1-97b1-bf1e6eb9e776" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_019ff673-f747-7cc2-8bae-4bcd77feff36" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_019ff673-f747-7cc2-8bae-4bcd77feff36" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_019ff673-f747-778a-8e84-d2eeb37cc002" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_019ff673-f747-778a-8e84-d2eeb37cc002" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdTradingDays_019ff673-f747-7d0f-9de4-983cd6e9c54b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentConvertibleThresholdTradingDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdTradingDays_019ff673-f747-7d0f-9de4-983cd6e9c54b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_019ff673-f747-756e-8661-01cfb638254e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_019ff673-f747-756e-8661-01cfb638254e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_DebtInstrumentConvertibleThresholdPercentageOfStockTradingPrice_019ff673-f747-71b0-ba98-c960452c357d" xlink:href="indv-20260930.xsd#indv_DebtInstrumentConvertibleThresholdPercentageOfStockTradingPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_indv_DebtInstrumentConvertibleThresholdPercentageOfStockTradingPrice_019ff673-f747-71b0-ba98-c960452c357d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_019ff673-f747-79ad-bd21-6b5c45503f0e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentConvertibleConversionRatio1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_019ff673-f747-79ad-bd21-6b5c45503f0e" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_DebtInstrumentConvertibleConversionPricePremiumOverSharePricePercentage_019ff673-f747-7517-8be3-868ce3c7c957" xlink:href="indv-20260930.xsd#indv_DebtInstrumentConvertibleConversionPricePremiumOverSharePricePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_indv_DebtInstrumentConvertibleConversionPricePremiumOverSharePricePercentage_019ff673-f747-7517-8be3-868ce3c7c957" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharePrice_019ff673-f747-7a32-b943-d2e52e742b0a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_us-gaap_SharePrice_019ff673-f747-7a32-b943-d2e52e742b0a" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleNumberOfEquityInstruments_019ff673-f747-7077-b7e5-6a7e4122cc6b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentConvertibleNumberOfEquityInstruments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_us-gaap_DebtInstrumentConvertibleNumberOfEquityInstruments_019ff673-f747-7077-b7e5-6a7e4122cc6b" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_DebtInstrumentConvertibleConversionValueTradingDays_019ff673-f747-70c7-972b-674132877605" xlink:href="indv-20260930.xsd#indv_DebtInstrumentConvertibleConversionValueTradingDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_indv_DebtInstrumentConvertibleConversionValueTradingDays_019ff673-f747-70c7-972b-674132877605" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_DebtInstrumentConvertibleRedemptionTradingDaysPriorToMaturity_019ff673-f747-7463-ba1c-bdc5fde2ba6b" xlink:href="indv-20260930.xsd#indv_DebtInstrumentConvertibleRedemptionTradingDaysPriorToMaturity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_indv_DebtInstrumentConvertibleRedemptionTradingDaysPriorToMaturity_019ff673-f747-7463-ba1c-bdc5fde2ba6b" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_019ff673-f747-7dde-892b-58dc90d0207a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentRedemptionPricePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_019ff673-f747-7dde-892b-58dc90d0207a" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019ff673-f747-71ae-95b9-2e8def2e649a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_us-gaap_LongTermDebt_019ff673-f747-71ae-95b9-2e8def2e649a" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_019ff673-f747-7411-98b4-290d93d3abbe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_019ff673-f747-7411-98b4-290d93d3abbe" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_019ff673-f747-706f-a996-7d76079d99f7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_019ff673-f747-706f-a996-7d76079d99f7" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_019ff673-f747-78c7-91c9-b95ac86796b2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_019ff673-f747-78c7-91c9-b95ac86796b2" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019ff673-f747-78bb-898f-52ead254c937" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019ff673-f747-7c88-8184-04af3b294a29" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019ff673-f747-78bb-898f-52ead254c937" xlink:type="arc" order="20"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://indivior.com/role/FinancialInstrumentsandFairValueMeasurementsDetails" xlink:type="simple" xlink:href="indv-20260930.xsd#FinancialInstrumentsandFairValueMeasurementsDetails"/>
  <link:definitionLink xlink:role="http://indivior.com/role/FinancialInstrumentsandFairValueMeasurementsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019ff673-f747-7842-a564-714e9bff9898" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019ff673-f747-7cef-b3ba-971e9793f366" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019ff673-f747-7842-a564-714e9bff9898" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019ff673-f747-7cef-b3ba-971e9793f366" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019ff673-f747-76fb-b5d2-b64277e2ce0c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019ff673-f747-7cef-b3ba-971e9793f366" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019ff673-f747-76fb-b5d2-b64277e2ce0c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019ff673-f747-76fb-b5d2-b64277e2ce0c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019ff673-f747-76fb-b5d2-b64277e2ce0c" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019ff673-f747-76fb-b5d2-b64277e2ce0c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019ff673-f747-7b7c-9cdc-af7894f2390e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019ff673-f747-76fb-b5d2-b64277e2ce0c" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019ff673-f747-7b7c-9cdc-af7894f2390e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019ff673-f747-7dcd-b2a7-f0b87cdd2f42" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019ff673-f747-7b7c-9cdc-af7894f2390e" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019ff673-f747-7dcd-b2a7-f0b87cdd2f42" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019ff673-f747-7ac1-9564-f469c351e681" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019ff673-f747-7b7c-9cdc-af7894f2390e" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019ff673-f747-7ac1-9564-f469c351e681" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesFairValue_019ff673-f747-7423-8621-139cae51ecc9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HeldToMaturitySecuritiesFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019ff673-f747-7842-a564-714e9bff9898" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesFairValue_019ff673-f747-7423-8621-139cae51ecc9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtFairValueDisclosures_019ff673-f747-7494-9835-fa94203f4200" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConvertibleDebtFairValueDisclosures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019ff673-f747-7842-a564-714e9bff9898" xlink:to="loc_us-gaap_ConvertibleDebtFairValueDisclosures_019ff673-f747-7494-9835-fa94203f4200" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://indivior.com/role/EarningsPerShareNarrativeDetails" xlink:type="simple" xlink:href="indv-20260930.xsd#EarningsPerShareNarrativeDetails"/>
  <link:definitionLink xlink:role="http://indivior.com/role/EarningsPerShareNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019ff673-f7db-73c1-8be5-07a031c6e660" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019ff673-f7db-70af-8ab4-6edc5740ffa2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019ff673-f7db-73c1-8be5-07a031c6e660" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019ff673-f7db-70af-8ab4-6edc5740ffa2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019ff673-f7db-74c9-a203-1d26f9fefb68" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019ff673-f7db-70af-8ab4-6edc5740ffa2" xlink:to="loc_us-gaap_DebtInstrumentAxis_019ff673-f7db-74c9-a203-1d26f9fefb68" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019ff673-f7db-74c9-a203-1d26f9fefb68_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019ff673-f7db-74c9-a203-1d26f9fefb68" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019ff673-f7db-74c9-a203-1d26f9fefb68_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019ff673-f7db-77ae-ba1b-6e95e30dd9c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019ff673-f7db-74c9-a203-1d26f9fefb68" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019ff673-f7db-77ae-ba1b-6e95e30dd9c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_ConvertibleSeniorNotesDue2031Member_019ff673-f7db-7cd1-a61d-f4a93afd6553" xlink:href="indv-20260930.xsd#indv_ConvertibleSeniorNotesDue2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019ff673-f7db-77ae-ba1b-6e95e30dd9c6" xlink:to="loc_indv_ConvertibleSeniorNotesDue2031Member_019ff673-f7db-7cd1-a61d-f4a93afd6553" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019ff673-f7db-7894-9783-1512ec2e5d4d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019ff673-f7db-70af-8ab4-6edc5740ffa2" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019ff673-f7db-7894-9783-1512ec2e5d4d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019ff673-f7db-7894-9783-1512ec2e5d4d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019ff673-f7db-7894-9783-1512ec2e5d4d" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019ff673-f7db-7894-9783-1512ec2e5d4d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019ff673-f7db-7484-bc67-76ccc35a46d5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019ff673-f7db-7894-9783-1512ec2e5d4d" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019ff673-f7db-7484-bc67-76ccc35a46d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_019ff673-f7db-7001-b0cd-174358fac486" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019ff673-f7db-7484-bc67-76ccc35a46d5" xlink:to="loc_us-gaap_ConvertibleDebtMember_019ff673-f7db-7001-b0cd-174358fac486" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_019ff673-f7db-77a2-899e-5f19d3515f14" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019ff673-f7db-73c1-8be5-07a031c6e660" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_019ff673-f7db-77a2-899e-5f19d3515f14" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToConversionOfDebtSecurities_019ff673-f7db-778b-afbf-4197a0a3e9b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncrementalCommonSharesAttributableToConversionOfDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019ff673-f7db-73c1-8be5-07a031c6e660" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToConversionOfDebtSecurities_019ff673-f7db-778b-afbf-4197a0a3e9b4" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://indivior.com/role/StockBasedPaymentsStockAwardActivityDetails" xlink:type="simple" xlink:href="indv-20260930.xsd#StockBasedPaymentsStockAwardActivityDetails"/>
  <link:definitionLink xlink:role="http://indivior.com/role/StockBasedPaymentsStockAwardActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ff673-f7db-770c-8ce1-7651956a3af0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ff673-f7db-7762-8175-00c557a86d0a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ff673-f7db-770c-8ce1-7651956a3af0" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ff673-f7db-7762-8175-00c557a86d0a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019ff673-f7db-7630-a62a-1c0b705549ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ff673-f7db-7762-8175-00c557a86d0a" xlink:to="loc_us-gaap_AwardTypeAxis_019ff673-f7db-7630-a62a-1c0b705549ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ff673-f7db-7630-a62a-1c0b705549ed_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019ff673-f7db-7630-a62a-1c0b705549ed" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ff673-f7db-7630-a62a-1c0b705549ed_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ff673-f7db-76b3-a150-8e6fc4cc2e2b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019ff673-f7db-7630-a62a-1c0b705549ed" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ff673-f7db-76b3-a150-8e6fc4cc2e2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_019ff673-f7db-716a-82c9-22114aa381a4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ff673-f7db-76b3-a150-8e6fc4cc2e2b" xlink:to="loc_us-gaap_RestrictedStockMember_019ff673-f7db-716a-82c9-22114aa381a4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_019ff673-f7db-7926-b480-5e19417bb1c8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ff673-f7db-76b3-a150-8e6fc4cc2e2b" xlink:to="loc_us-gaap_PerformanceSharesMember_019ff673-f7db-7926-b480-5e19417bb1c8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019ff673-f7db-71a0-802c-cb738fd68b15" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ff673-f7db-770c-8ce1-7651956a3af0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019ff673-f7db-71a0-802c-cb738fd68b15" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019ff673-f7db-739f-b207-135c6f8a1c7e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019ff673-f7db-71a0-802c-cb738fd68b15" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019ff673-f7db-739f-b207-135c6f8a1c7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019ff673-f7db-733e-a5b9-51ae694ae796" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019ff673-f7db-71a0-802c-cb738fd68b15" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019ff673-f7db-733e-a5b9-51ae694ae796" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019ff673-f7db-7c00-a935-87362d483037" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019ff673-f7db-71a0-802c-cb738fd68b15" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019ff673-f7db-7c00-a935-87362d483037" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsCanceledForfeitedOrAdjustedInPeriod_019ff673-f7db-7d1f-a383-12ddf35bf999" xlink:href="indv-20260930.xsd#indv_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsCanceledForfeitedOrAdjustedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019ff673-f7db-71a0-802c-cb738fd68b15" xlink:to="loc_indv_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsCanceledForfeitedOrAdjustedInPeriod_019ff673-f7db-7d1f-a383-12ddf35bf999" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019ff673-f7db-7412-b349-a30be214837b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://indivior.com/role/StockBasedPaymentsNarrativeDetails" xlink:type="simple" xlink:href="indv-20260930.xsd#StockBasedPaymentsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://indivior.com/role/StockBasedPaymentsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ff673-f7db-7a97-a72a-4dd48373b365" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ff673-f7db-7eca-8cad-852bb156af6d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ff673-f7db-7a97-a72a-4dd48373b365" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ff673-f7db-7eca-8cad-852bb156af6d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019ff673-f7db-7d97-8e7c-bc082cc0650f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ff673-f7db-7eca-8cad-852bb156af6d" xlink:to="loc_us-gaap_AwardTypeAxis_019ff673-f7db-7d97-8e7c-bc082cc0650f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ff673-f7db-7d97-8e7c-bc082cc0650f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019ff673-f7db-7d97-8e7c-bc082cc0650f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ff673-f7db-7d97-8e7c-bc082cc0650f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ff673-f7db-7e25-9e63-4ecaae17a3c5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019ff673-f7db-7d97-8e7c-bc082cc0650f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ff673-f7db-7e25-9e63-4ecaae17a3c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_RestrictedStockAndPerformanceSharesMember_019ff673-f7db-78d0-8eec-de2fbfa8f852" xlink:href="indv-20260930.xsd#indv_RestrictedStockAndPerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019ff673-f7db-7e25-9e63-4ecaae17a3c5" xlink:to="loc_indv_RestrictedStockAndPerformanceSharesMember_019ff673-f7db-78d0-8eec-de2fbfa8f852" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_019ff673-f7db-718c-98d7-aeab9ab15576" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_indv_RestrictedStockAndPerformanceSharesMember_019ff673-f7db-78d0-8eec-de2fbfa8f852" xlink:to="loc_us-gaap_RestrictedStockMember_019ff673-f7db-718c-98d7-aeab9ab15576" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_019ff673-f7db-78a0-a44c-b85477cb2921" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_indv_RestrictedStockAndPerformanceSharesMember_019ff673-f7db-78d0-8eec-de2fbfa8f852" xlink:to="loc_us-gaap_PerformanceSharesMember_019ff673-f7db-78a0-a44c-b85477cb2921" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019ff673-f7db-7998-bc2f-37376946d8f1" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019ff673-f7db-7eca-8cad-852bb156af6d" xlink:to="loc_srt_RangeAxis_019ff673-f7db-7998-bc2f-37376946d8f1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ff673-f7db-7998-bc2f-37376946d8f1_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019ff673-f7db-7998-bc2f-37376946d8f1" xlink:to="loc_srt_RangeMember_019ff673-f7db-7998-bc2f-37376946d8f1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ff673-f7db-7df3-8489-13f52c6e0d02" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019ff673-f7db-7998-bc2f-37376946d8f1" xlink:to="loc_srt_RangeMember_019ff673-f7db-7df3-8489-13f52c6e0d02" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019ff673-f7db-7694-a8e7-5e3f4a868790" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ff673-f7db-7df3-8489-13f52c6e0d02" xlink:to="loc_srt_MinimumMember_019ff673-f7db-7694-a8e7-5e3f4a868790" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019ff673-f7db-77f1-93c1-8562c093b8ae" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ff673-f7db-7df3-8489-13f52c6e0d02" xlink:to="loc_srt_MaximumMember_019ff673-f7db-77f1-93c1-8562c093b8ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019ff673-f7db-7365-9f43-f429a6363e92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ff673-f7db-7a97-a72a-4dd48373b365" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019ff673-f7db-7365-9f43-f429a6363e92" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019ff673-f7db-7ccb-aa23-203f441d7e30" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ff673-f7db-7a97-a72a-4dd48373b365" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019ff673-f7db-7ccb-aa23-203f441d7e30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_019ff673-f7db-7541-8787-bf0263115392" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ff673-f7db-7a97-a72a-4dd48373b365" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue_019ff673-f7db-7541-8787-bf0263115392" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsPercentageOfTarget_019ff673-f7db-718d-9f99-ae9053290348" xlink:href="indv-20260930.xsd#indv_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsPercentageOfTarget"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ff673-f7db-7a97-a72a-4dd48373b365" xlink:to="loc_indv_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsPercentageOfTarget_019ff673-f7db-718d-9f99-ae9053290348" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_019ff673-f7db-7a16-a764-30c67de5d792" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ff673-f7db-7a97-a72a-4dd48373b365" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_019ff673-f7db-7a16-a764-30c67de5d792" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_019ff673-f7db-7fa5-8842-cde61565a99d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019ff673-f7db-7a97-a72a-4dd48373b365" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_019ff673-f7db-7fa5-8842-cde61565a99d" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://indivior.com/role/CommitmentsandContingenciesDetails" xlink:type="simple" xlink:href="indv-20260930.xsd#CommitmentsandContingenciesDetails"/>
  <link:definitionLink xlink:role="http://indivior.com/role/CommitmentsandContingenciesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_019ff673-f7db-7b70-b522-aaf5e5125db5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_019ff673-f7db-75ca-aaf8-166279b3115f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_019ff673-f7db-7b70-b522-aaf5e5125db5" xlink:to="loc_us-gaap_LossContingenciesTable_019ff673-f7db-75ca-aaf8-166279b3115f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_019ff673-f7db-7f91-a2bd-80ac04f9f909" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019ff673-f7db-75ca-aaf8-166279b3115f" xlink:to="loc_srt_LitigationCaseAxis_019ff673-f7db-7f91-a2bd-80ac04f9f909" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_019ff673-f7db-7f91-a2bd-80ac04f9f909_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_019ff673-f7db-7f91-a2bd-80ac04f9f909" xlink:to="loc_srt_LitigationCaseTypeDomain_019ff673-f7db-7f91-a2bd-80ac04f9f909_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_019ff673-f7db-7cd4-97cd-07194edabe79" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_019ff673-f7db-7f91-a2bd-80ac04f9f909" xlink:to="loc_srt_LitigationCaseTypeDomain_019ff673-f7db-7cd4-97cd-07194edabe79" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_DentalAllegationsMDLMember_019ff673-f7db-720d-9e7c-06c60e762d68" xlink:href="indv-20260930.xsd#indv_DentalAllegationsMDLMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019ff673-f7db-7cd4-97cd-07194edabe79" xlink:to="loc_indv_DentalAllegationsMDLMember_019ff673-f7db-720d-9e7c-06c60e762d68" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_DentalAllegationsMDLScheduleAMember_019ff673-f7db-7528-9ee2-7bbf1f37bd4c" xlink:href="indv-20260930.xsd#indv_DentalAllegationsMDLScheduleAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019ff673-f7db-7cd4-97cd-07194edabe79" xlink:to="loc_indv_DentalAllegationsMDLScheduleAMember_019ff673-f7db-7528-9ee2-7bbf1f37bd4c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_DentalAllegationsStateCourtMember_019ff673-f7db-7880-98b8-d67a957d541c" xlink:href="indv-20260930.xsd#indv_DentalAllegationsStateCourtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019ff673-f7db-7cd4-97cd-07194edabe79" xlink:to="loc_indv_DentalAllegationsStateCourtMember_019ff673-f7db-7880-98b8-d67a957d541c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_CivilOpioidLitigationMDLStateAndSubdivisionMSAMember_019ff673-f7db-7c88-8e4d-55550f3412d1" xlink:href="indv-20260930.xsd#indv_CivilOpioidLitigationMDLStateAndSubdivisionMSAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019ff673-f7db-7cd4-97cd-07194edabe79" xlink:to="loc_indv_CivilOpioidLitigationMDLStateAndSubdivisionMSAMember_019ff673-f7db-7c88-8e4d-55550f3412d1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_CivilOpioidLitigationMember_01a15f7b-8abf-7a88-bc6e-493b47aa3ee0" xlink:href="indv-20260930.xsd#indv_CivilOpioidLitigationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019ff673-f7db-7cd4-97cd-07194edabe79" xlink:to="loc_indv_CivilOpioidLitigationMember_01a15f7b-8abf-7a88-bc6e-493b47aa3ee0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_CivilOpioidLitigationMDLNeonatalAbstinenceSyndromeMember_019ff673-f7db-76b2-9278-ac21cace6b0f" xlink:href="indv-20260930.xsd#indv_CivilOpioidLitigationMDLNeonatalAbstinenceSyndromeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019ff673-f7db-7cd4-97cd-07194edabe79" xlink:to="loc_indv_CivilOpioidLitigationMDLNeonatalAbstinenceSyndromeMember_019ff673-f7db-76b2-9278-ac21cace6b0f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_CivilOpioidLitigationMDLThirdPartyPayorMember_01a15f82-ba28-76b7-8f38-5e983ebc48ed" xlink:href="indv-20260930.xsd#indv_CivilOpioidLitigationMDLThirdPartyPayorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019ff673-f7db-7cd4-97cd-07194edabe79" xlink:to="loc_indv_CivilOpioidLitigationMDLThirdPartyPayorMember_01a15f82-ba28-76b7-8f38-5e983ebc48ed" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_CivilOpioidLitigationMDLIndividualPlaintiffsMember_019ff673-f7db-76c9-8e85-81c460f0bb51" xlink:href="indv-20260930.xsd#indv_CivilOpioidLitigationMDLIndividualPlaintiffsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019ff673-f7db-7cd4-97cd-07194edabe79" xlink:to="loc_indv_CivilOpioidLitigationMDLIndividualPlaintiffsMember_019ff673-f7db-76c9-8e85-81c460f0bb51" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_U.K.ShareholderClaimsFirstTrialMember_019ff673-f7db-7123-a3ba-3fe5bd40fd64" xlink:href="indv-20260930.xsd#indv_U.K.ShareholderClaimsFirstTrialMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019ff673-f7db-7cd4-97cd-07194edabe79" xlink:to="loc_indv_U.K.ShareholderClaimsFirstTrialMember_019ff673-f7db-7123-a3ba-3fe5bd40fd64" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_019ff673-f7db-7d61-8b74-a46e3143ea9e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019ff673-f7db-75ca-aaf8-166279b3115f" xlink:to="loc_srt_StatementScenarioAxis_019ff673-f7db-7d61-8b74-a46e3143ea9e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_019ff673-f7db-7d61-8b74-a46e3143ea9e_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_019ff673-f7db-7d61-8b74-a46e3143ea9e" xlink:to="loc_srt_ScenarioUnspecifiedDomain_019ff673-f7db-7d61-8b74-a46e3143ea9e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_019ff673-f7db-718e-a6a2-228aed128cf8" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_019ff673-f7db-7d61-8b74-a46e3143ea9e" xlink:to="loc_srt_ScenarioUnspecifiedDomain_019ff673-f7db-718e-a6a2-228aed128cf8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_019ff673-f7db-7bf3-8bcc-b6fdc65d0656" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_019ff673-f7db-718e-a6a2-228aed128cf8" xlink:to="loc_srt_ScenarioForecastMember_019ff673-f7db-7bf3-8bcc-b6fdc65d0656" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_01a15d9c-7aca-7d5a-bcb9-a18243f8e4a3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019ff673-f7db-75ca-aaf8-166279b3115f" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_01a15d9c-7aca-7d5a-bcb9-a18243f8e4a3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_01a15d9c-7aca-7d5a-bcb9-a18243f8e4a3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_01a15d9c-7aca-7d5a-bcb9-a18243f8e4a3" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_01a15d9c-7aca-7d5a-bcb9-a18243f8e4a3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_01a15d9c-7aca-73c8-8cdf-3ee50df0e5ae" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_01a15d9c-7aca-7d5a-bcb9-a18243f8e4a3" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_01a15d9c-7aca-73c8-8cdf-3ee50df0e5ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_01a15d9c-9085-742a-8960-811489a4b539" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_01a15d9c-7aca-73c8-8cdf-3ee50df0e5ae" xlink:to="loc_us-gaap_SubsequentEventMember_01a15d9c-9085-742a-8960-811489a4b539" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_01a15f76-b264-7ccb-b449-a09d479c43bc" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019ff673-f7db-75ca-aaf8-166279b3115f" xlink:to="loc_srt_RangeAxis_01a15f76-b264-7ccb-b449-a09d479c43bc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a15f76-b264-7ccb-b449-a09d479c43bc_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_01a15f76-b264-7ccb-b449-a09d479c43bc" xlink:to="loc_srt_RangeMember_01a15f76-b264-7ccb-b449-a09d479c43bc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a15f76-b264-75ad-9456-0857f84ab2e3" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_01a15f76-b264-7ccb-b449-a09d479c43bc" xlink:to="loc_srt_RangeMember_01a15f76-b264-75ad-9456-0857f84ab2e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_01a15f76-c95e-7b54-ab04-7bb98b24e157" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_01a15f76-b264-75ad-9456-0857f84ab2e3" xlink:to="loc_srt_MinimumMember_01a15f76-c95e-7b54-ab04-7bb98b24e157" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_01a15f7c-115e-7d9e-a031-65c7ae8d73fc" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019ff673-f7db-75ca-aaf8-166279b3115f" xlink:to="loc_srt_StatementGeographicalAxis_01a15f7c-115e-7d9e-a031-65c7ae8d73fc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_01a15f7c-115e-7d9e-a031-65c7ae8d73fc_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_01a15f7c-115e-7d9e-a031-65c7ae8d73fc" xlink:to="loc_srt_SegmentGeographicalDomain_01a15f7c-115e-7d9e-a031-65c7ae8d73fc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_01a15f7c-115e-71d5-97ab-f60fdc4137b8" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_01a15f7c-115e-7d9e-a031-65c7ae8d73fc" xlink:to="loc_srt_SegmentGeographicalDomain_01a15f7c-115e-71d5-97ab-f60fdc4137b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_stpr_MD_01a15f7c-37ae-7171-a36a-ccc9ff20edd0" xlink:href="https://xbrl.sec.gov/stpr/2026/stpr-2026.xsd#stpr_MD"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_01a15f7c-115e-71d5-97ab-f60fdc4137b8" xlink:to="loc_stpr_MD_01a15f7c-37ae-7171-a36a-ccc9ff20edd0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyPendingClaimsNumber_019ff673-f7db-7fb2-b539-e87ba1f30439" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingencyPendingClaimsNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019ff673-f7db-7b70-b522-aaf5e5125db5" xlink:to="loc_us-gaap_LossContingencyPendingClaimsNumber_019ff673-f7db-7fb2-b539-e87ba1f30439" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNumberOfPlaintiffs_019ff673-f7db-7950-91e5-dc05bbb589d8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingencyNumberOfPlaintiffs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019ff673-f7db-7b70-b522-aaf5e5125db5" xlink:to="loc_us-gaap_LossContingencyNumberOfPlaintiffs_019ff673-f7db-7950-91e5-dc05bbb589d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNewClaimsFiledNumber_019ff673-f7db-7ca3-b92b-aefe4a5d7c85" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingencyNewClaimsFiledNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019ff673-f7db-7b70-b522-aaf5e5125db5" xlink:to="loc_us-gaap_LossContingencyNewClaimsFiledNumber_019ff673-f7db-7ca3-b92b-aefe4a5d7c85" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_LossContingencyTolledClaimsNumberOfIndividuals_019ff673-f7db-72e8-8e35-62ec084a7669" xlink:href="indv-20260930.xsd#indv_LossContingencyTolledClaimsNumberOfIndividuals"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019ff673-f7db-7b70-b522-aaf5e5125db5" xlink:to="loc_indv_LossContingencyTolledClaimsNumberOfIndividuals_019ff673-f7db-72e8-8e35-62ec084a7669" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_LossContingencyClaimsFinalizedNumberOfStates_019ff673-f7db-721b-a6c5-23048aa14660" xlink:href="indv-20260930.xsd#indv_LossContingencyClaimsFinalizedNumberOfStates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019ff673-f7db-7b70-b522-aaf5e5125db5" xlink:to="loc_indv_LossContingencyClaimsFinalizedNumberOfStates_019ff673-f7db-721b-a6c5-23048aa14660" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_LossContingencyClaimsFinalizedNumberOfSubdivisions_019ff673-f7db-7ce6-a6f8-3aa06bf631f7" xlink:href="indv-20260930.xsd#indv_LossContingencyClaimsFinalizedNumberOfSubdivisions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019ff673-f7db-7b70-b522-aaf5e5125db5" xlink:to="loc_indv_LossContingencyClaimsFinalizedNumberOfSubdivisions_019ff673-f7db-7ce6-a6f8-3aa06bf631f7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationReserve_01a15f7a-5df8-758f-b5b7-b380a63ead8a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LitigationReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019ff673-f7db-7b70-b522-aaf5e5125db5" xlink:to="loc_us-gaap_LitigationReserve_01a15f7a-5df8-758f-b5b7-b380a63ead8a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyClaimsDismissedNumber_019ff673-f7db-7987-9c30-bf3226953494" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingencyClaimsDismissedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019ff673-f7db-7b70-b522-aaf5e5125db5" xlink:to="loc_us-gaap_LossContingencyClaimsDismissedNumber_019ff673-f7db-7987-9c30-bf3226953494" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_LossContingencyExpectedTrialPeriod_019ff673-f7db-7a55-a63b-e90e524cb4cf" xlink:href="indv-20260930.xsd#indv_LossContingencyExpectedTrialPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019ff673-f7db-7b70-b522-aaf5e5125db5" xlink:to="loc_indv_LossContingencyExpectedTrialPeriod_019ff673-f7db-7a55-a63b-e90e524cb4cf" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://indivior.com/role/RestructuringSummaryofRestructuringActivityDetails" xlink:type="simple" xlink:href="indv-20260930.xsd#RestructuringSummaryofRestructuringActivityDetails"/>
  <link:definitionLink xlink:role="http://indivior.com/role/RestructuringSummaryofRestructuringActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_019ff673-f7db-79cc-b8e8-8492be3f9f4f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019ff673-f7db-7d4a-9eff-046372c71809" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019ff673-f7db-79cc-b8e8-8492be3f9f4f" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019ff673-f7db-7d4a-9eff-046372c71809" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanAxis_019ff673-f7db-7bef-af46-abb619ca532b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringPlanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019ff673-f7db-7d4a-9eff-046372c71809" xlink:to="loc_us-gaap_RestructuringPlanAxis_019ff673-f7db-7bef-af46-abb619ca532b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_019ff673-f7db-7bef-af46-abb619ca532b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringPlanAxis_019ff673-f7db-7bef-af46-abb619ca532b" xlink:to="loc_us-gaap_RestructuringPlanDomain_019ff673-f7db-7bef-af46-abb619ca532b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_019ff673-f7db-7584-ad6d-c71b5b3fdc45" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringPlanAxis_019ff673-f7db-7bef-af46-abb619ca532b" xlink:to="loc_us-gaap_RestructuringPlanDomain_019ff673-f7db-7584-ad6d-c71b5b3fdc45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_IndiviorActionAgendaPhaseIMember_019ff673-f7db-7ee4-901f-a868c4e08a9e" xlink:href="indv-20260930.xsd#indv_IndiviorActionAgendaPhaseIMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringPlanDomain_019ff673-f7db-7584-ad6d-c71b5b3fdc45" xlink:to="loc_indv_IndiviorActionAgendaPhaseIMember_019ff673-f7db-7ee4-901f-a868c4e08a9e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_CeasePhase3DevelopmentOfINDV6001AndNotAdvanceINDV2000InternallyMember_019ff673-f7db-7c5b-a5c6-0df23fe41c68" xlink:href="indv-20260930.xsd#indv_CeasePhase3DevelopmentOfINDV6001AndNotAdvanceINDV2000InternallyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringPlanDomain_019ff673-f7db-7584-ad6d-c71b5b3fdc45" xlink:to="loc_indv_CeasePhase3DevelopmentOfINDV6001AndNotAdvanceINDV2000InternallyMember_019ff673-f7db-7c5b-a5c6-0df23fe41c68" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_019ff673-f7db-73ef-89a2-a4be93783564" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019ff673-f7db-7d4a-9eff-046372c71809" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_019ff673-f7db-73ef-89a2-a4be93783564" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_019ff673-f7db-73ef-89a2-a4be93783564_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_019ff673-f7db-73ef-89a2-a4be93783564" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_019ff673-f7db-73ef-89a2-a4be93783564_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_019ff673-f7db-7171-8232-89524fb02c48" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_019ff673-f7db-73ef-89a2-a4be93783564" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_019ff673-f7db-7171-8232-89524fb02c48" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_ContractTerminationAndRelatedExpensesAndImpairmentOfLongLivedAssetsMember_019ff673-f7db-7d64-976d-5540dfc824f3" xlink:href="indv-20260930.xsd#indv_ContractTerminationAndRelatedExpensesAndImpairmentOfLongLivedAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_019ff673-f7db-7171-8232-89524fb02c48" xlink:to="loc_indv_ContractTerminationAndRelatedExpensesAndImpairmentOfLongLivedAssetsMember_019ff673-f7db-7d64-976d-5540dfc824f3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_EmployeeSeveranceLegalConsultingAndOtherRestructuringMember_01a16a0a-9e51-77aa-af81-0171ec818a81" xlink:href="indv-20260930.xsd#indv_EmployeeSeveranceLegalConsultingAndOtherRestructuringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_019ff673-f7db-7171-8232-89524fb02c48" xlink:to="loc_indv_EmployeeSeveranceLegalConsultingAndOtherRestructuringMember_01a16a0a-9e51-77aa-af81-0171ec818a81" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveRollForward_019ff673-f7db-7f84-b22f-d4748b7ffbd7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringReserveRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019ff673-f7db-79cc-b8e8-8492be3f9f4f" xlink:to="loc_us-gaap_RestructuringReserveRollForward_019ff673-f7db-7f84-b22f-d4748b7ffbd7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveCurrent_019ff673-f7db-722e-b59d-7d76ce08e31b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringReserveCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_019ff673-f7db-7f84-b22f-d4748b7ffbd7" xlink:to="loc_us-gaap_RestructuringReserveCurrent_019ff673-f7db-722e-b59d-7d76ce08e31b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringSettlementAndImpairmentProvisions_019ff673-f7db-7aad-aa85-156674075b3f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringSettlementAndImpairmentProvisions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_019ff673-f7db-7f84-b22f-d4748b7ffbd7" xlink:to="loc_us-gaap_RestructuringSettlementAndImpairmentProvisions_019ff673-f7db-7aad-aa85-156674075b3f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRestructuring_019ff673-f7db-7704-9795-9568c4b9b71e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForRestructuring"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_019ff673-f7db-7f84-b22f-d4748b7ffbd7" xlink:to="loc_us-gaap_PaymentsForRestructuring_019ff673-f7db-7704-9795-9568c4b9b71e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_RestructuringReserveAdjustmentForNonCashExpense_019ff673-f7db-701a-91bd-042bd5060a59" xlink:href="indv-20260930.xsd#indv_RestructuringReserveAdjustmentForNonCashExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_019ff673-f7db-7f84-b22f-d4748b7ffbd7" xlink:to="loc_indv_RestructuringReserveAdjustmentForNonCashExpense_019ff673-f7db-701a-91bd-042bd5060a59" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveCurrent_019ff673-f7db-771d-9fb2-3ab9cbbbbf7c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringReserveCurrent"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://indivior.com/role/RestructuringNarrativeDetails" xlink:type="simple" xlink:href="indv-20260930.xsd#RestructuringNarrativeDetails"/>
  <link:definitionLink xlink:role="http://indivior.com/role/RestructuringNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_019ff673-f7db-7ba2-8581-b0b6d78c55c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019ff673-f7db-7235-9364-2f70caa8e213" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019ff673-f7db-7ba2-8581-b0b6d78c55c2" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019ff673-f7db-7235-9364-2f70caa8e213" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanAxis_019ff673-f7db-7308-9d9c-7409f8408b69" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringPlanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019ff673-f7db-7235-9364-2f70caa8e213" xlink:to="loc_us-gaap_RestructuringPlanAxis_019ff673-f7db-7308-9d9c-7409f8408b69" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_019ff673-f7db-7308-9d9c-7409f8408b69_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringPlanAxis_019ff673-f7db-7308-9d9c-7409f8408b69" xlink:to="loc_us-gaap_RestructuringPlanDomain_019ff673-f7db-7308-9d9c-7409f8408b69_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_019ff673-f7db-70d9-91a1-9ef3ee7a99e3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringPlanAxis_019ff673-f7db-7308-9d9c-7409f8408b69" xlink:to="loc_us-gaap_RestructuringPlanDomain_019ff673-f7db-70d9-91a1-9ef3ee7a99e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_IndiviorActionAgendaPhaseIMember_019ff673-f7db-70a2-a106-093d9d5c1594" xlink:href="indv-20260930.xsd#indv_IndiviorActionAgendaPhaseIMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringPlanDomain_019ff673-f7db-70d9-91a1-9ef3ee7a99e3" xlink:to="loc_indv_IndiviorActionAgendaPhaseIMember_019ff673-f7db-70a2-a106-093d9d5c1594" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_CeasePhase3DevelopmentOfINDV6001AndNotAdvanceINDV2000InternallyMember_019ff673-f7db-7c01-bc1e-1f4616f85454" xlink:href="indv-20260930.xsd#indv_CeasePhase3DevelopmentOfINDV6001AndNotAdvanceINDV2000InternallyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringPlanDomain_019ff673-f7db-70d9-91a1-9ef3ee7a99e3" xlink:to="loc_indv_CeasePhase3DevelopmentOfINDV6001AndNotAdvanceINDV2000InternallyMember_019ff673-f7db-7c01-bc1e-1f4616f85454" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfIncomeLocationBalanceAxis_019ff673-f7db-70b2-97a0-46e82ee58f70" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementOfIncomeLocationBalanceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019ff673-f7db-7235-9364-2f70caa8e213" xlink:to="loc_us-gaap_StatementOfIncomeLocationBalanceAxis_019ff673-f7db-70b2-97a0-46e82ee58f70" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_01a15f88-0ffc-7ea7-96c5-bb3d6835b870" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019ff673-f7db-7235-9364-2f70caa8e213" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_01a15f88-0ffc-7ea7-96c5-bb3d6835b870" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_01a15f88-0ffc-7ea7-96c5-bb3d6835b870_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_01a15f88-0ffc-7ea7-96c5-bb3d6835b870" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_01a15f88-0ffc-7ea7-96c5-bb3d6835b870_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_01a15f88-0ffc-7577-80e9-e64dce4eac59" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_01a15f88-0ffc-7ea7-96c5-bb3d6835b870" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_01a15f88-0ffc-7577-80e9-e64dce4eac59" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherRestructuringMember_01a15f88-cfc3-704c-9551-cecbd884c86b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherRestructuringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_01a15f88-0ffc-7577-80e9-e64dce4eac59" xlink:to="loc_us-gaap_OtherRestructuringMember_01a15f88-cfc3-704c-9551-cecbd884c86b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeSeveranceMember_01a15f88-0ffc-7dc2-9bb3-a1e4ea8866cd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeSeveranceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_01a15f88-0ffc-7577-80e9-e64dce4eac59" xlink:to="loc_us-gaap_EmployeeSeveranceMember_01a15f88-0ffc-7dc2-9bb3-a1e4ea8866cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedCostCostIncurredToDate1_019ff673-f7db-78a6-99d7-f386f6f3e538" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringAndRelatedCostCostIncurredToDate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019ff673-f7db-7ba2-8581-b0b6d78c55c2" xlink:to="loc_us-gaap_RestructuringAndRelatedCostCostIncurredToDate1_019ff673-f7db-78a6-99d7-f386f6f3e538" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringSettlementAndImpairmentProvisions_019ff673-f7db-744f-93b3-d7f8feb3af84" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringSettlementAndImpairmentProvisions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019ff673-f7db-7ba2-8581-b0b6d78c55c2" xlink:to="loc_us-gaap_RestructuringSettlementAndImpairmentProvisions_019ff673-f7db-744f-93b3-d7f8feb3af84" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedCostExpectedCostRemaining1_019ff673-f7db-789b-ae9a-d6f5b3fe3ddc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringAndRelatedCostExpectedCostRemaining1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019ff673-f7db-7ba2-8581-b0b6d78c55c2" xlink:to="loc_us-gaap_RestructuringAndRelatedCostExpectedCostRemaining1_019ff673-f7db-789b-ae9a-d6f5b3fe3ddc" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://indivior.com/role/RestructuringNarrativeDetails_1" xlink:type="simple" xlink:href="indv-20260930.xsd#RestructuringNarrativeDetails_1"/>
  <link:definitionLink xlink:role="http://indivior.com/role/RestructuringNarrativeDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_019ff673-f7db-7ba2-8581-b0b6d78c55c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019ff673-f7db-7235-9364-2f70caa8e213" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019ff673-f7db-7ba2-8581-b0b6d78c55c2" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019ff673-f7db-7235-9364-2f70caa8e213" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanAxis_019ff673-f7db-7308-9d9c-7409f8408b69" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringPlanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019ff673-f7db-7235-9364-2f70caa8e213" xlink:to="loc_us-gaap_RestructuringPlanAxis_019ff673-f7db-7308-9d9c-7409f8408b69" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_019ff673-f7db-7308-9d9c-7409f8408b69_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringPlanAxis_019ff673-f7db-7308-9d9c-7409f8408b69" xlink:to="loc_us-gaap_RestructuringPlanDomain_019ff673-f7db-7308-9d9c-7409f8408b69_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_019ff673-f7db-70d9-91a1-9ef3ee7a99e3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringPlanAxis_019ff673-f7db-7308-9d9c-7409f8408b69" xlink:to="loc_us-gaap_RestructuringPlanDomain_019ff673-f7db-70d9-91a1-9ef3ee7a99e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_IndiviorActionAgendaPhaseIMember_019ff673-f7db-70a2-a106-093d9d5c1594" xlink:href="indv-20260930.xsd#indv_IndiviorActionAgendaPhaseIMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringPlanDomain_019ff673-f7db-70d9-91a1-9ef3ee7a99e3" xlink:to="loc_indv_IndiviorActionAgendaPhaseIMember_019ff673-f7db-70a2-a106-093d9d5c1594" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_CeasePhase3DevelopmentOfINDV6001AndNotAdvanceINDV2000InternallyMember_019ff673-f7db-7c01-bc1e-1f4616f85454" xlink:href="indv-20260930.xsd#indv_CeasePhase3DevelopmentOfINDV6001AndNotAdvanceINDV2000InternallyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringPlanDomain_019ff673-f7db-70d9-91a1-9ef3ee7a99e3" xlink:to="loc_indv_CeasePhase3DevelopmentOfINDV6001AndNotAdvanceINDV2000InternallyMember_019ff673-f7db-7c01-bc1e-1f4616f85454" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_01a15f88-0ffc-7ea7-96c5-bb3d6835b870" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019ff673-f7db-7235-9364-2f70caa8e213" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_01a15f88-0ffc-7ea7-96c5-bb3d6835b870" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_01a15f88-0ffc-7ea7-96c5-bb3d6835b870_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_01a15f88-0ffc-7ea7-96c5-bb3d6835b870" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_01a15f88-0ffc-7ea7-96c5-bb3d6835b870_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_01a15f88-0ffc-7577-80e9-e64dce4eac59" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_01a15f88-0ffc-7ea7-96c5-bb3d6835b870" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_01a15f88-0ffc-7577-80e9-e64dce4eac59" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherRestructuringMember_01a15f88-cfc3-704c-9551-cecbd884c86b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherRestructuringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_01a15f88-0ffc-7577-80e9-e64dce4eac59" xlink:to="loc_us-gaap_OtherRestructuringMember_01a15f88-cfc3-704c-9551-cecbd884c86b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeSeveranceMember_01a15f88-0ffc-7dc2-9bb3-a1e4ea8866cd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeSeveranceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_01a15f88-0ffc-7577-80e9-e64dce4eac59" xlink:to="loc_us-gaap_EmployeeSeveranceMember_01a15f88-0ffc-7dc2-9bb3-a1e4ea8866cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedCostCostIncurredToDate1_019ff673-f7db-78a6-99d7-f386f6f3e538" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringAndRelatedCostCostIncurredToDate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019ff673-f7db-7ba2-8581-b0b6d78c55c2" xlink:to="loc_us-gaap_RestructuringAndRelatedCostCostIncurredToDate1_019ff673-f7db-78a6-99d7-f386f6f3e538" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringSettlementAndImpairmentProvisions_019ff673-f7db-744f-93b3-d7f8feb3af84" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringSettlementAndImpairmentProvisions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019ff673-f7db-7ba2-8581-b0b6d78c55c2" xlink:to="loc_us-gaap_RestructuringSettlementAndImpairmentProvisions_019ff673-f7db-744f-93b3-d7f8feb3af84" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedCostExpectedCostRemaining1_019ff673-f7db-789b-ae9a-d6f5b3fe3ddc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringAndRelatedCostExpectedCostRemaining1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019ff673-f7db-7ba2-8581-b0b6d78c55c2" xlink:to="loc_us-gaap_RestructuringAndRelatedCostExpectedCostRemaining1_019ff673-f7db-789b-ae9a-d6f5b3fe3ddc" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://indivior.com/role/SubsequentEventsDetails" xlink:type="simple" xlink:href="indv-20260930.xsd#SubsequentEventsDetails"/>
  <link:definitionLink xlink:role="http://indivior.com/role/SubsequentEventsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_019ff673-f7db-7b8c-94c0-4c00e9f65cf7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_019ff673-f7db-7ff3-a02a-ed3a8fc8e99a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_019ff673-f7db-7b8c-94c0-4c00e9f65cf7" xlink:to="loc_us-gaap_SubsequentEventTable_019ff673-f7db-7ff3-a02a-ed3a8fc8e99a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_01a11d7d-18b4-73de-985a-67559b48c04d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019ff673-f7db-7ff3-a02a-ed3a8fc8e99a" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_01a11d7d-18b4-73de-985a-67559b48c04d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_01a11d7d-18b4-73de-985a-67559b48c04d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_01a11d7d-18b4-73de-985a-67559b48c04d" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_01a11d7d-18b4-73de-985a-67559b48c04d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_01a11d7d-18b4-7e0a-8f46-c52d2135b47f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_01a11d7d-18b4-73de-985a-67559b48c04d" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_01a11d7d-18b4-7e0a-8f46-c52d2135b47f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_01a11d7d-3754-7892-9773-38c4e25b2648" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_01a11d7d-18b4-7e0a-8f46-c52d2135b47f" xlink:to="loc_us-gaap_SubsequentEventMember_01a11d7d-3754-7892-9773-38c4e25b2648" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_01a16a13-0950-7202-a1fa-04579f30043a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019ff673-f7db-7ff3-a02a-ed3a8fc8e99a" xlink:to="loc_srt_StatementScenarioAxis_01a16a13-0950-7202-a1fa-04579f30043a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_01a16a13-0950-7202-a1fa-04579f30043a_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_01a16a13-0950-7202-a1fa-04579f30043a" xlink:to="loc_srt_ScenarioUnspecifiedDomain_01a16a13-0950-7202-a1fa-04579f30043a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_01a16a13-0950-7c7b-8981-ef4ea66e1af7" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_01a16a13-0950-7202-a1fa-04579f30043a" xlink:to="loc_srt_ScenarioUnspecifiedDomain_01a16a13-0950-7c7b-8981-ef4ea66e1af7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_01a16a13-2128-73e8-8b43-9f28cde7a0f8" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_01a16a13-0950-7c7b-8981-ef4ea66e1af7" xlink:to="loc_srt_ScenarioForecastMember_01a16a13-2128-73e8-8b43-9f28cde7a0f8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_01a16a0f-9729-7e93-9e8e-6b94e651ad30" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019ff673-f7db-7ff3-a02a-ed3a8fc8e99a" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_01a16a0f-9729-7e93-9e8e-6b94e651ad30" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_01a16a0f-9729-7e93-9e8e-6b94e651ad30_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_01a16a0f-9729-7e93-9e8e-6b94e651ad30" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_01a16a0f-9729-7e93-9e8e-6b94e651ad30_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_01a16a0f-9729-76f9-a8b5-5ced77202dfe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_01a16a0f-9729-7e93-9e8e-6b94e651ad30" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_01a16a0f-9729-76f9-a8b5-5ced77202dfe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember_01a16a11-3b3e-778d-b715-3cb9b7b85b99" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_01a16a0f-9729-76f9-a8b5-5ced77202dfe" xlink:to="loc_us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember_01a16a11-3b3e-778d-b715-3cb9b7b85b99" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_01a16a0f-b889-78a8-81c2-820008e17c5d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019ff673-f7db-7ff3-a02a-ed3a8fc8e99a" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_01a16a0f-b889-78a8-81c2-820008e17c5d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_01a16a0f-b889-78a8-81c2-820008e17c5d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_01a16a0f-b889-78a8-81c2-820008e17c5d" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_01a16a0f-b889-78a8-81c2-820008e17c5d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_01a16a0f-b889-7a27-9607-7a7cb6ab9e34" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_01a16a0f-b889-78a8-81c2-820008e17c5d" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_01a16a0f-b889-7a27-9607-7a7cb6ab9e34" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_SUBUTEXTabletBusinessFranceAndGermanyMember_01a16a10-de5c-75d0-addd-6c0b03e99921" xlink:href="indv-20260930.xsd#indv_SUBUTEXTabletBusinessFranceAndGermanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_01a16a0f-b889-7a27-9607-7a7cb6ab9e34" xlink:to="loc_indv_SUBUTEXTabletBusinessFranceAndGermanyMember_01a16a10-de5c-75d0-addd-6c0b03e99921" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_01a16a16-3da0-7bf1-b9f0-895ed1bc89ad" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019ff673-f7db-7ff3-a02a-ed3a8fc8e99a" xlink:to="loc_srt_ProductOrServiceAxis_01a16a16-3da0-7bf1-b9f0-895ed1bc89ad" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_01a16a16-3da0-7bf1-b9f0-895ed1bc89ad_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_01a16a16-3da0-7bf1-b9f0-895ed1bc89ad" xlink:to="loc_srt_ProductsAndServicesDomain_01a16a16-3da0-7bf1-b9f0-895ed1bc89ad_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_01a16a16-3da0-7925-9ff5-0c8faeada13c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_01a16a16-3da0-7bf1-b9f0-895ed1bc89ad" xlink:to="loc_srt_ProductsAndServicesDomain_01a16a16-3da0-7925-9ff5-0c8faeada13c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_SUBUTEXMember_01a16a16-8270-724c-bed1-9ddd986151d0" xlink:href="indv-20260930.xsd#indv_SUBUTEXMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_01a16a16-3da0-7925-9ff5-0c8faeada13c" xlink:to="loc_indv_SUBUTEXMember_01a16a16-8270-724c-bed1-9ddd986151d0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_01a16a16-9e06-7608-8799-ef9d77e59730" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019ff673-f7db-7ff3-a02a-ed3a8fc8e99a" xlink:to="loc_srt_StatementGeographicalAxis_01a16a16-9e06-7608-8799-ef9d77e59730" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_01a16a16-9e06-7608-8799-ef9d77e59730_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_01a16a16-9e06-7608-8799-ef9d77e59730" xlink:to="loc_srt_SegmentGeographicalDomain_01a16a16-9e06-7608-8799-ef9d77e59730_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_01a16a16-9e06-73e2-876c-25213189dc3b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_01a16a16-9e06-7608-8799-ef9d77e59730" xlink:to="loc_srt_SegmentGeographicalDomain_01a16a16-9e06-73e2-876c-25213189dc3b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_FranceAndGermanyMember_01a16a16-d976-7ca4-b96d-f345e1c7bc9a" xlink:href="indv-20260930.xsd#indv_FranceAndGermanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_01a16a16-9e06-73e2-876c-25213189dc3b" xlink:to="loc_indv_FranceAndGermanyMember_01a16a16-d976-7ca4-b96d-f345e1c7bc9a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a179b4-df84-71c4-a14a-aa6e33c28d93" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019ff673-f7db-7ff3-a02a-ed3a8fc8e99a" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a179b4-df84-71c4-a14a-aa6e33c28d93" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a179b4-df84-71c4-a14a-aa6e33c28d93_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a179b4-df84-71c4-a14a-aa6e33c28d93" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a179b4-df84-71c4-a14a-aa6e33c28d93_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a179b4-df84-753d-802e-c79696416421" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a179b4-df84-71c4-a14a-aa6e33c28d93" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a179b4-df84-753d-802e-c79696416421" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerProductAndServiceBenchmarkMember_01a179b5-1da6-781d-823d-1f3403aa84f0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerProductAndServiceBenchmarkMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a179b4-df84-753d-802e-c79696416421" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerProductAndServiceBenchmarkMember_01a179b5-1da6-781d-823d-1f3403aa84f0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_01a179b5-5c6f-7f64-8b78-de0b81b844c3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019ff673-f7db-7ff3-a02a-ed3a8fc8e99a" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_01a179b5-5c6f-7f64-8b78-de0b81b844c3" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_01a179b5-5c6f-7f64-8b78-de0b81b844c3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_01a179b5-5c6f-7f64-8b78-de0b81b844c3" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_01a179b5-5c6f-7f64-8b78-de0b81b844c3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_01a179b5-5c6f-7fa5-9885-1643200aa2ac" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_01a179b5-5c6f-7f64-8b78-de0b81b844c3" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_01a179b5-5c6f-7fa5-9885-1643200aa2ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductConcentrationRiskMember_01a179b5-9a92-7eef-bfa5-a84dc4347f88" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProductConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_01a179b5-5c6f-7fa5-9885-1643200aa2ac" xlink:to="loc_us-gaap_ProductConcentrationRiskMember_01a179b5-9a92-7eef-bfa5-a84dc4347f88" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_01a11d7c-b24a-75eb-97d8-a4dc3669cee4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019ff673-f7db-7b8c-94c0-4c00e9f65cf7" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_01a11d7c-b24a-75eb-97d8-a4dc3669cee4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_01a16a0d-c94b-7b28-94fe-c736411623dc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019ff673-f7db-7b8c-94c0-4c00e9f65cf7" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_01a16a0d-c94b-7b28-94fe-c736411623dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_indv_DisposalGroupIncludingDiscontinuedOperationConsiderationPercentagePaidAtClosing_01a16a0e-b803-7590-9586-fb55376cbb58" xlink:href="indv-20260930.xsd#indv_DisposalGroupIncludingDiscontinuedOperationConsiderationPercentagePaidAtClosing"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019ff673-f7db-7b8c-94c0-4c00e9f65cf7" xlink:to="loc_indv_DisposalGroupIncludingDiscontinuedOperationConsiderationPercentagePaidAtClosing_01a16a0e-b803-7590-9586-fb55376cbb58" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_01a179b4-76f6-7e66-a487-b201af424ef1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019ff673-f7db-7b8c-94c0-4c00e9f65cf7" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_01a179b4-76f6-7e66-a487-b201af424ef1" xlink:type="arc" order="3"/>
  </link:definitionLink>
</link:linkbase>
