Exhibit 4.1

NUMBER

F

COMMON STOCK

FORTINET, INC.

SHARES

COMMON STOCK

THIS CERTIFICATE IS TRANSFERABLE IN JERSEY CITY, NJ, NEW YORK, NY

AND PITTSBURGH, PA

INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE

SEE REVERSE FOR CERTAIN DEFINITIONS

CUSIP 34959E 10 9

This Certifies that

is the record holder of

FULLY PAID AND NONASSESSABLE SHARES OF THE COMMON STOCK OF, PAR VALUE OF $0.001 PER SHARE,

FORTINET, INC.

transferable on the books of the Corporation by the holder hereof, in person or by duly authorized attorney upon surrender of this Certificate properly endorsed. This Certificate is not valid unless countersigned by the Transfer Agent and registered by the Registrar.

Witness the facsimile seal of the Corporation and the facsimile signatures of its duly authorized officers.

Dated

VICE PRESIDENT AND GENERAL COUNSEL

PRESIDENT AND CHIEF EXECUTIVE OFFICER

COUNTERSIGNED AND REGISTERED:

MELLON INVESTOR SERVICES LLC

TRANSFER AGENT AND REGISTRAR BY:

AUTHORIZED SIGNATURE

The following abbreviations, when used in the inscription on the face of this certificate, shall be construed as though they were written out in full according to applicable laws or regulations:

TEN COM – as tenants in common

TEN ENT – as tenants by the entireties

JT TEN – as joint tenants with right of survivorship and not as tenants in common

UNIF GIFT MIN ACT – ......................... Custodian .........................

(Cust) (Minor) under Uniform Gifts to Minors Act (State)

UNIF TRF MIN ACT – ................. Custodian (until age ................) (Cust) ............................ under Uniform Transfers (Minor) to Minors Act (State)

Additional abbreviations may also be used though not in the above list.

FOR VALUE RECEIVED, hereby sell, assign and transfer unto

PLEASE INSERT SOCIAL SECURITY OR OTHER IDENTIFYING NUMBER OF ASSIGNEE

(PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING ZIP CODE, OF ASSIGNEE)

Shares

of the common stock represented by the within Certificate, and do hereby irrevocably constitute and appoint

Attorney

to transfer the said stock on the books of the within named Corporation with full power of substitution in the premises.

Dated

NOTICE:

THE SIGNATURE TO THIS ASSIGNMENT MUST CORRESPOND WITH THE NAME AS WRITTEN UPON THE FACE OF THE CERTIFICATE IN EVERY PARTICULAR, WITHOUT ALTERATION OR ENLARGEMENT OR ANY CHANGE WHATEVER.

Signature(s) Guaranteed:

THE SIGNATURE(S) SHOULD BE GUARANTEED BY AN ELIGIBLE GUARANTOR INSTITUTION (BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH MEMBERSHIP IN AN APPROVED MEDALLION SIGNATURE GUARANTEE PROGRAM), PURSUANT TO S.E.C. RULE 17Ad-15.

KEEP THIS CERTIFICATE IN A SAFE PLACE. IF IT IS LOST, STOLEN, MUTILATED OR DESTROYED, THE CORPORATION WILL REQUIRE A BOND OF INDEMNITY AS A CONDITION TO THE ISSUANCE OF A REPLACEMENT CERTIFICATE.