<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/nport" xmlns:com="http://www.sec.gov/edgar/common" xmlns:ncom="http://www.sec.gov/edgar/nportcommon" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.sec.gov/edgar/nport eis_NPORT_Filer.xsd">
  <headerData>
    <submissionType>NPORT-P</submissionType>
    <isConfidential>false</isConfidential>
    <filerInfo>

      <filer>
        <issuerCredentials>
          <cik>0001330967</cik>
          <ccc>XXXXXXXX</ccc>
        </issuerCredentials>
      </filer>


      <seriesClassInfo>
        <seriesId>S000002504</seriesId>
        <classId>C000006820</classId>
        <classId>C000006821</classId>
        <classId>C000006822</classId>
        <classId>C000006823</classId>
        <classId>C000006824</classId>
        <classId>C000006826</classId>
        <classId>C000006827</classId>
        <classId>C000006828</classId>
        <classId>C000173227</classId>
      </seriesClassInfo>


    </filerInfo>
  </headerData>
  <formData>
    <genInfo>
      <regName>MFS SERIES TRUST XII</regName>
      <regFileNumber>811-21780</regFileNumber>
      <regCik>0001330967</regCik>
      <regLei>549300VVIIPRJRW6FR46</regLei>
      <regStreet1>111 HUNTINGTON AVENUE</regStreet1>
      <regCity>BOSTON</regCity>
      <regStateConditional regCountry="US" regState="US-MA"/>
      <regZipOrPostalCode>02199</regZipOrPostalCode>
      <regPhone>617-954-5000</regPhone>
      <seriesName>MFS Lifetime 2030 Fund</seriesName>
      <seriesId>S000002504</seriesId>
      <seriesLei>549300VPT7TXX8JRMU69</seriesLei>
      <repPdEnd>2026-04-30</repPdEnd>
      <repPdDate>2026-01-31</repPdDate>
      <isFinalFiling>N</isFinalFiling>
    </genInfo>
    <fundInfo>
      <totAssets>730860564.30</totAssets>
      <totLiabs>643786.08</totLiabs>
      <netAssets>730216778.22</netAssets>
      <assetsAttrMiscSec>0.00000000</assetsAttrMiscSec>
      <assetsInvested>0.00000000</assetsInvested>
      <amtPayOneYrBanksBorr>0.00000000</amtPayOneYrBanksBorr>
      <amtPayOneYrCtrldComp>0.00000000</amtPayOneYrCtrldComp>
      <amtPayOneYrOthAffil>0.00000000</amtPayOneYrOthAffil>
      <amtPayOneYrOther>0.00000000</amtPayOneYrOther>
      <amtPayAftOneYrBanksBorr>0.00000000</amtPayAftOneYrBanksBorr>
      <amtPayAftOneYrCtrldComp>0.00000000</amtPayAftOneYrCtrldComp>
      <amtPayAftOneYrOthAffil>0.00000000</amtPayAftOneYrOthAffil>
      <amtPayAftOneYrOther>0.00000000</amtPayAftOneYrOther>
      <delayDeliv>0.00000000</delayDeliv>
      <standByCommit>0.00000000</standByCommit>
      <liquidPref>0.00000000</liquidPref>
      <cshNotRptdInCorD>0.00000000</cshNotRptdInCorD>
      <isNonCashCollateral>N</isNonCashCollateral>
      <returnInfo>
        <monthlyTotReturns>
          <monthlyTotReturn classId="C000006820" rtn1="0.64000000" rtn2="0.18000000" rtn3="1.52000000"/>
          <monthlyTotReturn classId="C000006821" rtn1="0.65000000" rtn2="0.10000000" rtn3="1.45000000"/>
          <monthlyTotReturn classId="C000006822" rtn1="0.60000000" rtn2="0.13000000" rtn3="1.48000000"/>
          <monthlyTotReturn classId="C000006823" rtn1="0.64000000" rtn2="0.25000000" rtn3="1.57000000"/>
          <monthlyTotReturn classId="C000006824" rtn1="0.59000000" rtn2="0.08000000" rtn3="1.53000000"/>
          <monthlyTotReturn classId="C000006826" rtn1="0.65000000" rtn2="0.14000000" rtn3="1.53000000"/>
          <monthlyTotReturn classId="C000006827" rtn1="0.65000000" rtn2="0.15000000" rtn3="1.59000000"/>
          <monthlyTotReturn classId="C000006828" rtn1="0.69000000" rtn2="0.20000000" rtn3="1.56000000"/>
          <monthlyTotReturn classId="C000173227" rtn1="0.70000000" rtn2="0.20000000" rtn3="1.57000000"/>
        </monthlyTotReturns>
        <othMon1 netRealizedGain="1737614.74000000" netUnrealizedAppr="1789362.02000000"/>
        <othMon2 netRealizedGain="1291727.54000000" netUnrealizedAppr="-24752852.04000000"/>
        <othMon3 netRealizedGain="1165001.79000000" netUnrealizedAppr="8927359.03000000"/>
      </returnInfo>
      <mon1Flow redemption="23120751.22000000" reinvestment="0.00000000" sales="7190477.76000000"/>
      <mon2Flow redemption="15108880.74000000" reinvestment="56532821.44000000" sales="12589345.76000000"/>
      <mon3Flow redemption="25134294.33000000" reinvestment="0.00000000" sales="8514587.02000000"/>



    </fundInfo>
    <invstOrSecs>
      <invstOrSec>
        <name>MFS New Discovery Fund</name>
        <lei>ZVEMRLDGMDO1D1VDSU87</lei>
        <title>MFS New Discovery Fund</title>
        <cusip>55273H346</cusip>
        <identifiers>
          <isin value="US55273H3460"/>
        </identifiers>
        <balance>96389.39000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>3524959.81000000</valUSD>
        <pctVal>0.482727857690</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Value Fund</name>
        <lei>HV6C0RMURVKFUQ3UTB42</lei>
        <title>MFS Value Fund</title>
        <cusip>55273H353</cusip>
        <identifiers>
          <isin value="US55273H3536"/>
        </identifiers>
        <balance>416541.43000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>21476876.23000000</valUSD>
        <pctVal>2.941164441928</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Research International Fund</name>
        <lei>UH91KW1VFNZQF5FY7237</lei>
        <title>MFS Research International Fund</title>
        <cusip>55273H361</cusip>
        <identifiers>
          <isin value="US55273H3619"/>
        </identifiers>
        <balance>568706.53000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>15514314.06000000</valUSD>
        <pctVal>2.124617582441</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Mid Cap Value Fund</name>
        <lei>BXHSCSBXYY1DOHP6E209</lei>
        <title>MFS Mid Cap Value Fund</title>
        <cusip>55273W475</cusip>
        <identifiers>
          <isin value="US55273W4758"/>
        </identifiers>
        <balance>439440.94000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>14259858.41000000</valUSD>
        <pctVal>1.952825357527</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Blended Research Core Equity Fund</name>
        <lei>SQK3NYUBFBKJ3GF1IO09</lei>
        <title>MFS Blended Research Core Equity Fund</title>
        <cusip>55273W483</cusip>
        <identifiers>
          <isin value="US55273W4832"/>
        </identifiers>
        <balance>470260.99000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>18876275.94000000</valUSD>
        <pctVal>2.585023585189</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Blended Research Mid Cap Equity Fund</name>
        <lei>549300CJNZTXTE7DBK33</lei>
        <title>MFS Blended Research Mid Cap Equity Fund</title>
        <cusip>552743551</cusip>
        <identifiers>
          <isin value="US5527435516"/>
        </identifiers>
        <balance>1840709.43000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>28218075.50000000</valUSD>
        <pctVal>3.864342253102</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Blended Research Small Cap Equity Fund</name>
        <lei>549300R0MISDFKQQMH05</lei>
        <title>MFS Blended Research Small Cap Equity Fund</title>
        <cusip>552743684</cusip>
        <identifiers>
          <isin value="US5527436845"/>
        </identifiers>
        <balance>459276.60000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>7109601.71000000</valUSD>
        <pctVal>0.973628917063</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Blended Research Growth Equity Fund</name>
        <lei>549300M0GLI3GVVPMM34</lei>
        <title>MFS Blended Research Growth Equity Fund</title>
        <cusip>552743783</cusip>
        <identifiers>
          <isin value="US5527437835"/>
        </identifiers>
        <balance>676572.24000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>18666628.05000000</valUSD>
        <pctVal>2.556313221876</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Global Opportunistic Bond Fund</name>
        <lei>XE280U8NKIY4V6K1JN70</lei>
        <title>MFS Global Opportunistic Bond Fund</title>
        <cusip>552743882</cusip>
        <identifiers>
          <isin value="US5527438825"/>
        </identifiers>
        <balance>6216715.39000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>51101400.47000000</valUSD>
        <pctVal>6.998113710091</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Blended Research Value Equity Fund</name>
        <lei>549300QL66OEPI6JSE90</lei>
        <title>MFS Blended Research Value Equity Fund</title>
        <cusip>552746133</cusip>
        <identifiers>
          <isin value="US5527461330"/>
        </identifiers>
        <balance>1304101.81000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>21543761.84000000</valUSD>
        <pctVal>2.950324134227</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Emerging Markets Debt Local Currency Fund</name>
        <lei>5493001KPK8UJ27DMD68</lei>
        <title>MFS Emerging Markets Debt Local Currency Fund</title>
        <cusip>552746323</cusip>
        <identifiers>
          <isin value="US5527463237"/>
        </identifiers>
        <balance>2318209.91000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>14210626.77000000</valUSD>
        <pctVal>1.946083299351</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS International Intrinsic Value Fund</name>
        <lei>7540QFSKYNTDFH7HAK24</lei>
        <title>MFS International Intrinsic Value Fund</title>
        <cusip>552746349</cusip>
        <identifiers>
          <isin value="US5527463492"/>
        </identifiers>
        <balance>164061.59000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>7527145.93000000</valUSD>
        <pctVal>1.030809775194</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS International Growth Fund</name>
        <lei>PTNAY8DC4VJYOKVJ5B83</lei>
        <title>MFS International Growth Fund</title>
        <cusip>552746356</cusip>
        <identifiers>
          <isin value="US5527463567"/>
        </identifiers>
        <balance>152762.08000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>7494507.84000000</valUSD>
        <pctVal>1.026340131251</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Emerging Markets Debt Fund</name>
        <lei>509D6AOZZ4SJ08T5BZ82</lei>
        <title>MFS Emerging Markets Debt Fund</title>
        <cusip>552746364</cusip>
        <identifiers>
          <isin value="US5527463641"/>
        </identifiers>
        <balance>1107397.09000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>14185756.68000000</valUSD>
        <pctVal>1.942677449096</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Research Bond Fund</name>
        <lei>FJAEEQMSDDUK9QL2E558</lei>
        <title>MFS Research Bond Fund</title>
        <cusip>55274K603</cusip>
        <identifiers>
          <isin value="US55274K6038"/>
        </identifiers>
        <balance>11192165.41000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>107892474.51000000</valUSD>
        <pctVal>14.77540337720</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Ltd Maturity Fund</name>
        <lei>7ER38PJ2TK60L3Y32478</lei>
        <title>MFS Ltd Maturity Fund</title>
        <cusip>55274K801</cusip>
        <identifiers>
          <isin value="US55274K8018"/>
        </identifiers>
        <balance>13137004.33000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>77508325.52000000</valUSD>
        <pctVal>10.61442681568</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Inflation Adjusted Bond Fund</name>
        <lei>VOHO802M9IKG3IZTEN75</lei>
        <title>MFS Inflation Adjusted Bond Fund</title>
        <cusip>55274K884</cusip>
        <identifiers>
          <isin value="US55274K8844"/>
        </identifiers>
        <balance>8049455.47000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>73169550.22000000</valUSD>
        <pctVal>10.02025047936</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Commodity Strategy Fund</name>
        <lei>T0OEQ8I3F6DXUJCOV412</lei>
        <title>MFS Commodity Strategy Fund</title>
        <cusip>55276T826</cusip>
        <identifiers>
          <isin value="US55276T8264"/>
        </identifiers>
        <balance>3690916.99000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>14616031.30000000</valUSD>
        <pctVal>2.001601679932</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Institutional Money Market Portfolio</name>
        <lei>5L2W638H85N8T1136O07</lei>
        <title>MFS Institutional Money Market Portfolio</title>
        <cusip>55291X109</cusip>
        <identifiers>
          <isin value="US55291X1090"/>
        </identifiers>
        <balance>10834917.95000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>10837084.93000000</valUSD>
        <pctVal>1.484091471633</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Research Fund</name>
        <lei>XFPOOG2XVG5TW1LZ8588</lei>
        <title>MFS Research Fund</title>
        <cusip>552981391</cusip>
        <identifiers>
          <isin value="US5529813918"/>
        </identifiers>
        <balance>331814.89000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>18813904.43000000</valUSD>
        <pctVal>2.576482079179</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS New Discovery Value Fund</name>
        <lei>LRMRW30Z8FYTIFW1W860</lei>
        <title>MFS New Discovery Value Fund</title>
        <cusip>552982696</cusip>
        <identifiers>
          <isin value="US5529826969"/>
        </identifiers>
        <balance>200888.72000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>3571801.42000000</valUSD>
        <pctVal>0.489142611692</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Government Securities Fund</name>
        <lei>UWWK6TDSOPDQSQMMEB12</lei>
        <title>MFS Government Securities Fund</title>
        <cusip>552982712</cusip>
        <identifiers>
          <isin value="US5529827124"/>
        </identifiers>
        <balance>8382828.54000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>72930608.26000000</valUSD>
        <pctVal>9.987528421050</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Global Real Estate Fund</name>
        <lei>ROYDM6SL56ZXYAENS860</lei>
        <title>MFS Global Real Estate Fund</title>
        <cusip>552982720</cusip>
        <identifiers>
          <isin value="US5529827207"/>
        </identifiers>
        <balance>888778.73000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>14655961.19000000</valUSD>
        <pctVal>2.007069904053</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS High Income Fund</name>
        <lei>DMVGFZCV67YA34LSI126</lei>
        <title>MFS High Income Fund</title>
        <cusip>552984684</cusip>
        <identifiers>
          <isin value="US5529846843"/>
        </identifiers>
        <balance>8937774.95000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>28153991.10000000</valUSD>
        <pctVal>3.855566174284</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Growth Fund</name>
        <lei>K4ZYIH3WSXKUSPKIPM59</lei>
        <title>MFS Growth Fund</title>
        <cusip>552985673</cusip>
        <identifiers>
          <isin value="US5529856735"/>
        </identifiers>
        <balance>94140.70000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>18536303.63000000</valUSD>
        <pctVal>2.538465861491</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Blended Research International Equity Fund</name>
        <lei>254900SJDP6D81SAVM86</lei>
        <title>MFS Blended Research International Equity Fund</title>
        <cusip>552987448</cusip>
        <identifiers>
          <isin value="US5529874480"/>
        </identifiers>
        <balance>1659754.58000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>30771849.88000000</valUSD>
        <pctVal>4.214070505885</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MFS Mid Cap Growth Fund</name>
        <lei>XPX0WXKIO6CLKBLYF666</lei>
        <title>MFS Mid Cap Growth Fund</title>
        <cusip>552987554</cusip>
        <identifiers>
          <isin value="US5529875545"/>
        </identifiers>
        <balance>492280.90000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>13911858.18000000</valUSD>
        <pctVal>1.905168245231</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
    </invstOrSecs>
    <explntrNotes>
      <explntrNote note="Monthly returns presented in Item B.5(a) have been calculated without deducting any applicable sales loads or redemption fees." noteItem="B.5.a"/>
    </explntrNotes>
    <signature>
      <ncom:dateSigned>2026-02-27</ncom:dateSigned>
      <ncom:nameOfApplicant>MFS SERIES TRUST XII</ncom:nameOfApplicant>
      <ncom:signature>James Byrne</ncom:signature>
      <ncom:signerName>James Byrne</ncom:signerName>
      <ncom:title>Assistant Treasurer</ncom:title>
    </signature>
  </formData>
  <documents>XXXX</documents>
</edgarSubmission>
