<SEC-DOCUMENT>0001144215-17-000110.txt : 20171030
<SEC-HEADER>0001144215-17-000110.hdr.sgml : 20171030
<ACCEPTANCE-DATETIME>20171030165932
ACCESSION NUMBER:		0001144215-17-000110
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20171026
FILED AS OF DATE:		20171030
DATE AS OF CHANGE:		20171030

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			NAGEL VERNON J
		CENTRAL INDEX KEY:			0001183398

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-16583
		FILM NUMBER:		171163056

	MAIL ADDRESS:	
		STREET 1:		1170 PEACHTREE STREET NE
		STREET 2:		SUITE 2300
		CITY:			ATLANTA
		STATE:			2Q
		ZIP:			30309

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ACUITY BRANDS INC
		CENTRAL INDEX KEY:			0001144215
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTRIC LIGHTING & WIRING EQUIPMENT [3640]
		IRS NUMBER:				582632672
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0831

	BUSINESS ADDRESS:	
		STREET 1:		1170 PEACHTREE STREET, NE
		STREET 2:		SUITE 2300
		CITY:			ATLANTA
		STATE:			GA
		ZIP:			30309-7676
		BUSINESS PHONE:		404-853-1400

	MAIL ADDRESS:	
		STREET 1:		1170 PEACHTREE STREET, NE
		STREET 2:		SUITE 2300
		CITY:			ATLANTA
		STATE:			GA
		ZIP:			30309-7676

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	L&C SPINCO INC
		DATE OF NAME CHANGE:	20010629
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_150939715904583.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-10-26</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001144215</issuerCik>
        <issuerName>ACUITY BRANDS INC</issuerName>
        <issuerTradingSymbol>AYI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001183398</rptOwnerCik>
            <rptOwnerName>NAGEL VERNON J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1170 PEACHTREE STREET NE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 2300</rptOwnerStreet2>
            <rptOwnerCity>ATLANTA</rptOwnerCity>
            <rptOwnerState>GA</rptOwnerState>
            <rptOwnerZipCode>30309</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chairman, President, and CEO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2017-10-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1866</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>158.69</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>207438</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2017-10-27</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1923</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>159.21</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>205515</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The transaction(s) reported relate(s) to the vesting of restricted stock held by the reporting person.</footnote>
        <footnote id="F2">The total direct shares owned includes 30,908time-vesting restricted shares.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Jill A. Gilmer, under Power of Attorney for Vernon J. Nagel</signatureName>
        <signatureDate>2017-10-30</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
