<SEC-DOCUMENT>0001567619-18-001321.txt : 20180816
<SEC-HEADER>0001567619-18-001321.hdr.sgml : 20180816
<ACCEPTANCE-DATETIME>20180816194213
ACCESSION NUMBER:		0001567619-18-001321
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20180815
FILED AS OF DATE:		20180816
DATE AS OF CHANGE:		20180816

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Hsieh Ming
		CENTRAL INDEX KEY:			0001302110

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-34511
		FILM NUMBER:		181024396

	MAIL ADDRESS:	
		STREET 1:		209 FAIR OAKS AVE
		CITY:			SOUTH PASADENA
		STATE:			CA
		ZIP:			91030

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			FORTINET INC
		CENTRAL INDEX KEY:			0001262039
		STANDARD INDUSTRIAL CLASSIFICATION:	COMPUTER PERIPHERAL EQUIPMENT, NEC [3577]
		IRS NUMBER:				770560389
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		899 KIFER ROAD
		CITY:			SUNNYVALE
		STATE:			CA
		ZIP:			94086
		BUSINESS PHONE:		408-235-7700

	MAIL ADDRESS:	
		STREET 1:		899 KIFER ROAD
		CITY:			SUNNYVALE
		STATE:			CA
		ZIP:			94086
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-08-15</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001262039</issuerCik>
        <issuerName>FORTINET INC</issuerName>
        <issuerTradingSymbol>FTNT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001302110</rptOwnerCik>
            <rptOwnerName>Hsieh Ming</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O FORTINET, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>899 KIFER ROAD</rptOwnerStreet2>
            <rptOwnerCity>SUNNYVALE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94086</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2018-08-15</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3592</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>3592</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3592</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Each restricted stock unit (&quot;RSU&quot;) represents a contingent right to receive one share of the Issuer's common stock.</footnote>
        <footnote id="F2">100% of the RSUs vest on June 22, 2019, subject to the continuing service of the Reporting Person on the vesting date. Shares of the Issuer's common stock will be delivered to the Reporting Person upon vesting.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ John Whittle, by power of attorney</signatureName>
        <signatureDate>2018-08-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
