<?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>S000038775</seriesId>
        <classId>C000119439</classId>
        <classId>C000119440</classId>
        <classId>C000119441</classId>
        <classId>C000119442</classId>
        <classId>C000119443</classId>
        <classId>C000119444</classId>
        <classId>C000119445</classId>
        <classId>C000119446</classId>
        <classId>C000173232</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 2045 Fund</seriesName>
      <seriesId>S000038775</seriesId>
      <seriesLei>54930078W14TCCY5W445</seriesLei>
      <repPdEnd>2026-04-30</repPdEnd>
      <repPdDate>2026-01-31</repPdDate>
      <isFinalFiling>N</isFinalFiling>
    </genInfo>
    <fundInfo>
      <totAssets>572429202.54</totAssets>
      <totLiabs>962581.05</totLiabs>
      <netAssets>571466621.49</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="C000119439" rtn1="0.82000000" rtn2="0.53000000" rtn3="3.15000000"/>
          <monthlyTotReturn classId="C000119440" rtn1="0.74000000" rtn2="0.48000000" rtn3="3.09000000"/>
          <monthlyTotReturn classId="C000119441" rtn1="0.75000000" rtn2="0.47000000" rtn3="3.05000000"/>
          <monthlyTotReturn classId="C000119442" rtn1="0.86000000" rtn2="0.53000000" rtn3="3.18000000"/>
          <monthlyTotReturn classId="C000119443" rtn1="0.78000000" rtn2="0.47000000" rtn3="3.07000000"/>
          <monthlyTotReturn classId="C000119444" rtn1="0.78000000" rtn2="0.49000000" rtn3="3.16000000"/>
          <monthlyTotReturn classId="C000119445" rtn1="0.87000000" rtn2="0.53000000" rtn3="3.11000000"/>
          <monthlyTotReturn classId="C000119446" rtn1="0.86000000" rtn2="0.55000000" rtn3="3.17000000"/>
          <monthlyTotReturn classId="C000173232" rtn1="0.86000000" rtn2="0.58000000" rtn3="3.18000000"/>
        </monthlyTotReturns>
        <othMon1 netRealizedGain="1277349.09000000" netUnrealizedAppr="3102416.11000000"/>
        <othMon2 netRealizedGain="344330.25000000" netUnrealizedAppr="-32822387.82000000"/>
        <othMon3 netRealizedGain="497815.64000000" netUnrealizedAppr="16893608.10000000"/>
      </returnInfo>
      <mon1Flow redemption="13735200.83000000" reinvestment="0.00000000" sales="5739224.04000000"/>
      <mon2Flow redemption="9693457.96000000" reinvestment="37250311.54000000" sales="9799259.10000000"/>
      <mon3Flow redemption="12577160.86000000" reinvestment="0.00000000" sales="5940112.63000000"/>



    </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>171515.44000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>6272319.46000000</valUSD>
        <pctVal>1.097582820085</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>581550.45000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>29984741.20000000</valUSD>
        <pctVal>5.246980326133</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>816545.54000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>22275362.36000000</valUSD>
        <pctVal>3.897928859243</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>834071.13000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>27065608.27000000</valUSD>
        <pctVal>4.736166077282</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>656964.99000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>26370574.50000000</valUSD>
        <pctVal>4.614543266104</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>3496273.91000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>53597879.07000000</valUSD>
        <pctVal>9.379004311792</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>816954.28000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>12646452.30000000</valUSD>
        <pctVal>2.212981795336</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>986377.06000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>27214143.03000000</valUSD>
        <pctVal>4.762157929546</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>1088378.71000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>8946473.01000000</valUSD>
        <pctVal>1.565528531950</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>1830826.96000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>30245261.45000000</valUSD>
        <pctVal>5.292568334287</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>982445.39000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>6022390.22000000</valUSD>
        <pctVal>1.053848115275</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 Equity Fund</name>
        <lei>GLINMRWNKCBOHYKQ2131</lei>
        <title>MFS Emerging Markets Equity Fund</title>
        <cusip>552746331</cusip>
        <identifiers>
          <isin value="US5527463310"/>
        </identifiers>
        <balance>90764.59000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>4368499.57000000</valUSD>
        <pctVal>0.764436522750</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>381149.51000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>17487139.43000000</valUSD>
        <pctVal>3.060045639132</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>353164.34000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>17326242.47000000</valUSD>
        <pctVal>3.031890545912</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>700281.85000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>8970610.54000000</valUSD>
        <pctVal>1.569752318448</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>1352081.72000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>13034067.81000000</valUSD>
        <pctVal>2.280809993069</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>2380499.37000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>21638739.30000000</valUSD>
        <pctVal>3.786527241710</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>6688557.75000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>26486688.68000000</valUSD>
        <pctVal>4.634861894635</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>8438943.85000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>8440631.64000000</valUSD>
        <pctVal>1.477012186292</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 New Discovery Fund</name>
        <lei>RC53GXLQZ5LVIZBRHR66</lei>
        <title>MFS International New Discovery Fund</title>
        <cusip>552981383</cusip>
        <identifiers>
          <isin value="US5529813835"/>
        </identifiers>
        <balance>495240.20000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>17273978.07000000</valUSD>
        <pctVal>3.022744884900</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>463828.35000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>26299067.39000000</valUSD>
        <pctVal>4.602030355059</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>359020.48000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>6383384.15000000</valUSD>
        <pctVal>1.117017846704</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>1551458.31000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>25583547.60000000</valUSD>
        <pctVal>4.476822729085</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>3779044.41000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>11903989.89000000</valUSD>
        <pctVal>2.083059524799</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>137375.66000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>27049266.67000000</valUSD>
        <pctVal>4.733306487695</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 Emerging Markets Equity Fund</name>
        <lei>549300N4Y1QEM5QDU861</lei>
        <title>MFS Blended Research Emerging Markets Equity Fund</title>
        <cusip>552987240</cusip>
        <identifiers>
          <isin value="US5529872401"/>
        </identifiers>
        <balance>225039.12000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>4446772.97000000</valUSD>
        <pctVal>0.778133455704</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>3117599.80000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>57800300.37000000</valUSD>
        <pctVal>10.11437907244</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>925010.13000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>26140786.27000000</valUSD>
        <pctVal>4.574333003359</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>
