<SEC-DOCUMENT>0001053507-25-000064.txt : 20250312
<SEC-HEADER>0001053507-25-000064.hdr.sgml : 20250312
<ACCEPTANCE-DATETIME>20250312165726
ACCESSION NUMBER:		0001053507-25-000064
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20250310
FILED AS OF DATE:		20250312
DATE AS OF CHANGE:		20250312

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			REED JOANN A
		CENTRAL INDEX KEY:			0001252013
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-14195
		FILM NUMBER:		25732471

	MAIL ADDRESS:	
		STREET 1:		C/O AMERICAN TOWER CORP
		STREET 2:		116 HUNTINGTON AVENUE
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			AMERICAN TOWER CORP /MA/
		CENTRAL INDEX KEY:			0001053507
		STANDARD INDUSTRIAL CLASSIFICATION:	REAL ESTATE INVESTMENT TRUSTS [6798]
		ORGANIZATION NAME:           	05 Real Estate & Construction
		IRS NUMBER:				650723837
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		116 HUNTINGTON AVE
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116
		BUSINESS PHONE:		6173757500

	MAIL ADDRESS:	
		STREET 1:		116 HUNTINGTON AVE
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	AMERICAN TOWER SYSTEMS CORP
		DATE OF NAME CHANGE:	19980128
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wk-form4_1741813039.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-03-10</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001053507</issuerCik>
        <issuerName>AMERICAN TOWER CORP /MA/</issuerName>
        <issuerTradingSymbol>AMT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001252013</rptOwnerCik>
            <rptOwnerName>REED JOANN A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>116 HUNTINGTON AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-03-10</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1056</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>62940</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">These restricted stock units (&quot;RSUs&quot;) were granted pursuant to the 2007 Equity Incentive Plan, as amended, and vest on March 10, 2026. Each RSU represents a contingent right to receive one share of Common Stock.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Marina A. Breed, as attorney-in-fact</signatureName>
        <signatureDate>2025-03-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>