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    <headerData>
        <submissionType>144</submissionType>
        <filerInfo>
            <filer>
                <filerCredentials>
                    <cik>0001767177</cik>
                    <ccc>XXXXXXXX</ccc>
                </filerCredentials>
            </filer>
            <liveTestFlag>LIVE</liveTestFlag>



        </filerInfo>
    </headerData>
    <formData>
        <issuerInfo>
            <issuerCik>0001022671</issuerCik>
            <issuerName>STEEL DYNAMICS INC.</issuerName>
            <secFileNumber>000-21719</secFileNumber>
            <issuerAddress>
                <ns2:street1>7575 West Jefferson Blvd.</ns2:street1>
                <ns2:city>Fort Wayne</ns2:city>
                <ns2:stateOrCountry>IN</ns2:stateOrCountry>
                <ns2:zipCode>46804</ns2:zipCode>
            </issuerAddress>
            <issuerContactPhone>(260) 969-3500</issuerContactPhone>
            <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>MIGUEL ALVAREZ</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
            <relationshipsToIssuer>
                <relationshipToIssuer>Officer</relationshipToIssuer>
            </relationshipsToIssuer>
        </issuerInfo>
        <securitiesInformation>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <brokerOrMarketmakerDetails>
                <name>Morgan Stanley Smith Barney LLC Executive Financial Services</name>
                <address>
                    <ns2:street1>1 New York Plaza</ns2:street1>
                    <ns2:street2>8th Floor</ns2:street2>
                    <ns2:city>New York</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10004</ns2:zipCode>
                </address>
            </brokerOrMarketmakerDetails>
            <noOfUnitsSold>7495</noOfUnitsSold>
            <aggregateMarketValue>1013808.93</aggregateMarketValue>
            <noOfUnitsOutstanding>148453876</noOfUnitsOutstanding>
            <approxSaleDate>05/20/2025</approxSaleDate>
            <securitiesExchangeName>NASDAQ</securitiesExchangeName>
        </securitiesInformation>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>02/25/2024</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted stock vesting under a registered plan</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>842</amountOfSecuritiesAcquired>
            <paymentDate>02/25/2024</paymentDate>
            <natureOfPayment>Not Applicable</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>02/24/2024</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted stock vesting under a registered plan</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>2096</amountOfSecuritiesAcquired>
            <paymentDate>02/24/2024</paymentDate>
            <natureOfPayment>Not Applicable</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>11/21/2024</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted stock vesting under a registered plan</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>291</amountOfSecuritiesAcquired>
            <paymentDate>11/21/2024</paymentDate>
            <natureOfPayment>Not Applicable</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>02/24/2025</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted stock vesting under a registered plan</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>2098</amountOfSecuritiesAcquired>
            <paymentDate>02/24/2025</paymentDate>
            <natureOfPayment>Not Applicable</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>11/22/2024</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted stock vesting under a registered plan</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>1325</amountOfSecuritiesAcquired>
            <paymentDate>11/22/2024</paymentDate>
            <natureOfPayment>Not Applicable</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>02/25/2025</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted stock vesting under a registered plan</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>843</amountOfSecuritiesAcquired>
            <paymentDate>02/25/2025</paymentDate>
            <natureOfPayment>Not Applicable</natureOfPayment>
        </securitiesToBeSold>
        <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
        <noticeSignature>
            <noticeDate>05/20/2025</noticeDate>
            <planAdoptionDates/>
            <signature>/s/ Miguel Alvarez</signature>
        </noticeSignature>
    </formData>
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144
0001767177
XXXXXXXX
LIVE
0001022671
STEEL DYNAMICS INC.
000-21719
7575 West Jefferson Blvd.
Fort Wayne
IN
46804
(260) 969-3500
MIGUEL ALVAREZ
Officer
Common
Morgan Stanley Smith Barney LLC Executive Financial Services
1 New York Plaza
8th Floor
New York
NY
10004
7495
1013808.93
148453876
05/20/2025
NASDAQ
Common
02/25/2024
Restricted stock vesting under a registered plan
Issuer
N
842
02/25/2024
Not Applicable
Common
02/24/2024
Restricted stock vesting under a registered plan
Issuer
N
2096
02/24/2024
Not Applicable
Common
11/21/2024
Restricted stock vesting under a registered plan
Issuer
N
291
11/21/2024
Not Applicable
Common
02/24/2025
Restricted stock vesting under a registered plan
Issuer
N
2098
02/24/2025
Not Applicable
Common
11/22/2024
Restricted stock vesting under a registered plan
Issuer
N
1325
11/22/2024
Not Applicable
Common
02/25/2025
Restricted stock vesting under a registered plan
Issuer
N
843
02/25/2025
Not Applicable
Y
05/20/2025
/s/ Miguel Alvarez