<PAGE>
                                                                     EXHIBIT 4.1

ALIGN TECHNOLOGY, INC.

INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE


THIS CERTIFICATE IS TRANSFERABLE
IN CANTON, MA AND NEW YORK, NY


SEE REVERSE FOR CERTAIN DEFINITIONS


CUSIP 016255 10 1

This certifies that
is the record holder of
FULLY PAID AND NONASSESSABLE SHARES OF COMMON STOCK, $0.0001 PAR VALUE, OF ALIGN
TECHNOLOGY, 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 until 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:


SECRETARY

CHAIRMAN



COUNTERSIGNED AND REGISTERED:
EQUISERVE TRUST COMPANY, N.A.
TRANSFER AGENT AND REGISTRAR

BY
AUTHORIZED SIGNATURE

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The Corporation shall furnish without charge to each stockholder who so requests
a statement of the powers, designations, preferences and relative,
participating, optional, or other special rights of each class of stock of the
Corporation or series thereof and the qualifications, limitations or
restrictions of such preferences and/or rights. Such requests shall be made to
the Corporation's Secretary at the principal office of the Corporation.

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:

<TABLE>
<CAPTION>
<S>                     <C>
        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)
</TABLE>

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

    For Value Received,               hereby sell(s), assign(s) and transfer(s)
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
X
X
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

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