<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-03-15</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000097216</issuerCik>
        <issuerName>TEREX CORP</issuerName>
        <issuerTradingSymbol>TEX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001830953</rptOwnerCik>
            <rptOwnerName>JOHNSTON STEPHEN</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O TEREX CORP</rptOwnerStreet1>
            <rptOwnerStreet2>301 MERRITT 7</rptOwnerStreet2>
            <rptOwnerCity>NORWALK</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06851</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>VP CAO and Controller</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, $.01 par value</value>
            </securityTitle>
            <transactionDate>
                <value>2025-03-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>5058</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>19370</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, $.01 par value</value>
            </securityTitle>
            <transactionDate>
                <value>2025-03-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1686</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>21056</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, $.01 par value</value>
            </securityTitle>
            <transactionDate>
                <value>2025-03-17</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1597</value>
                    <footnoteId id="F4"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>40.31</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>19459</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The shares represent 5058 restricted stock units (&quot;RSUs&quot;) issued by Issuer pursuant to one of its long-term incentive plans. Each RSU represents a contingent right to receive one share of the Issuer's common stock. The RSUs will vest as follows: 1/3 on March 15, 2026; 1/3 on March 15, 2027; and 1/3 on March 15, 2028, subject to the Reporting Person's continued employment with the Issuer on each such vesting date.</footnote>
        <footnote id="F2">Total includes reported restricted stock units.</footnote>
        <footnote id="F3">The shares represent 1686 restricted stock units (&quot;RSUs&quot;) issued by Issuer pursuant to one of its long-term incentive plans. Each RSU represents a contingent right to receive one share of the Issuer's common stock. The RSUs will vest in the first quarter of 2028 if the Company achieves a targeted return on invested capital (&quot;ROIC&quot;) in each of 2025, 2026 and 2027. The number of RSUs in this grant are subject to adjustment, up or down, based upon attainment above or below the targeted ROIC.</footnote>
        <footnote id="F4">Shares are being withheld for payment of the tax liability associated with the scheduled vesting of previously granted restricted stock awards.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/Scott J. Posner, by power of attorney</signatureName>
        <signatureDate>2025-03-18</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0508
4
2025-03-15
0
0000097216
TEREX CORP
TEX
0001830953
JOHNSTON STEPHEN
C/O TEREX CORP
301 MERRITT 7
NORWALK
CT
06851
0
1
0
0
VP CAO and Controller
0
Common Stock, $.01 par value
2025-03-15
4
A
0
5058
0
A
19370
D
Common Stock, $.01 par value
2025-03-15
4
A
0
1686
0
A
21056
D
Common Stock, $.01 par value
2025-03-17
4
F
0
1597
40.31
D
19459
D
The shares represent 5058 restricted stock units ("RSUs") issued by Issuer pursuant to one of its long-term incentive plans. Each RSU represents a contingent right to receive one share of the Issuer's common stock. The RSUs will vest as follows: 1/3 on March 15, 2026; 1/3 on March 15, 2027; and 1/3 on March 15, 2028, subject to the Reporting Person's continued employment with the Issuer on each such vesting date.
Total includes reported restricted stock units.
The shares represent 1686 restricted stock units ("RSUs") issued by Issuer pursuant to one of its long-term incentive plans. Each RSU represents a contingent right to receive one share of the Issuer's common stock. The RSUs will vest in the first quarter of 2028 if the Company achieves a targeted return on invested capital ("ROIC") in each of 2025, 2026 and 2027. The number of RSUs in this grant are subject to adjustment, up or down, based upon attainment above or below the targeted ROIC.
Shares are being withheld for payment of the tax liability associated with the scheduled vesting of previously granted restricted stock awards.
/s/Scott J. Posner, by power of attorney
2025-03-18