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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2016-02-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001649338</issuerCik>
        <issuerName>Broadcom Ltd</issuerName>
        <issuerTradingSymbol>AVGO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001142524</rptOwnerCik>
            <rptOwnerName>HARTENSTEIN EDDY W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O AVAGO TECHNOLOGIES US INC.</rptOwnerStreet1>
            <rptOwnerStreet2>1320 RIDDER PARK DRIVE</rptOwnerStreet2>
            <rptOwnerCity>SAN JOSE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>95131</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Ordinary Shares, no par value</value>
            </securityTitle>
            <transactionDate>
                <value>2016-02-01</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>31648</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>31648</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Ordinary Shares, no par value</value>
            </securityTitle>
            <transactionDate>
                <value>2016-02-01</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>262</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>31910</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Acquired in connection with the transactions consummated on February 1, 2016 pursuant to the terms of an Agreement and Plan of Merger, dated as of May 28, 2015 (the &quot;Merger Agreement&quot;), by and among the Issuer, Avago Technologies Limited (&quot;Avago&quot;), Broadcom Corporation (&quot;Broadcom&quot;), Safari Cayman L.P., Avago Technologies Cayman Holdings Ltd., Avago Technologies Cayman Finance Limited, Buffalo CS Merger Sub, Inc. (&quot;CS Merger Sub&quot;) and Buffalo UT Merger Sub, Inc. (&quot;UT Merger Sub,&quot; and, together with CS Merger Sub, the &quot;Merger Subs&quot;), pursuant to which (a) the Issuer indirectly acquired Avago pursuant to the terms of a scheme of arrangement under Singapore law consummated in accordance with Section 210 of the Companies Act (Chapter 50) of Singapore, and (b) the Merger Subs merged with and into Broadcom, with Broadcom as the surviving corporation in such mergers (collectively, the &quot;Transactions&quot;). Continued in footnote (2).</footnote>
        <footnote id="F2">At the effective time of the Transactions, each share of Broadcom common stock (each, a &quot;Broadcom Common Share&quot;) was converted into the right to receive, at the election of the holder of such Broadcom Common Share, and subject to proration in accordance with the Merger Agreement, (i) $54.50 in cash, (ii) 0.4378 freely-tradeable ordinary shares of Holdco, or (iii) 0.4378 limited partnership units of Holdco LP, that are designed to be the economic equivalent of 0.4378 ordinary shares of Holdco.</footnote>
        <footnote id="F3">Grant of 262 Restricted Share Units (&quot;RSUs&quot;).  Upon vesting therof, the Reporting Person is entitled to receive one (1) ordinary share for each one (1) RSU. The RSUs vest in full on the first anniversary of February 1, 2016, subject to the Reporting Person's continuing service on the vesting date.</footnote>
        <footnote id="F4">Includes 262 RSUs.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Patricia McCall, Attorney-in-Fact for Eddy W. Hartenstein</signatureName>
        <signatureDate>2016-02-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
