Exhibit 4.1


 


	 	NUMBER OF UNITS

U-
	SEE REVERSE FOR CERTAIN

DEFINITIONS	CUSIP: G4035N 111


 


GP-Act III Acquisition Corp.


 


UNITS CONSISTING OF ONE CLASS A ORDINARY
SHARE AND ONE-THIRD OF ONE REDEEMABLE WARRANT, EACH WHOLE WARRANT ENTITLING THE HOLDER TO PURCHASE ONE CLASS A ORDINARY SHARE


 


	THIS CERTIFIES THAT	is the owner of	Units.


 


Each Unit (“Unit”) consists of one (1) Class
A Ordinary Share, par value $0.0001 per share (“Class A Ordinary Shares”), of GP-Act III Acquisition Corp.,
a Cayman Islands exempted company (the “Company”), and one-third (1/3) of one redeemable warrant (the “Warrant”).
Each whole Warrant entitles the holder to purchase one (1) Class A Ordinary Share (subject to adjustment) for $11.50 per share
(subject to adjustment). Only whole Warrants are exercisable. Each Warrant will become exercisable on the later of (i) thirty (30)
days after the Company’s completion of a merger, share exchange, asset acquisition, share purchase, reorganization or other
similar business combination with one or more businesses (each a “Business Combination”), and (ii) twelve (12)
months from the closing of the Company’s initial public offering, and will expire, unless exercised before 5:00 p.m., New
York City Time, on the date that is five (5) years after the date on which the Company completes its initial Business Combination,
or earlier upon redemption or liquidation. The Class A Ordinary Shares and Warrants comprising the Units represented by this
certificate will begin separate trading on [•], 2021 unless Citigroup Global Markets Inc. elects to allow separate trading
earlier, subject to the Company’s filing of a Current Report on Form 8-K with the Securities and Exchange Commission containing
an audited balance sheet reflecting the Company’s receipt of the gross proceeds of its initial public offering and issuing
a press release announcing when separate trading will begin. No fractional Warrants will be issued upon separation of the Units.
The terms of the Warrants are governed by a Warrant Agreement, dated as of March [•], 2021, between the Company and Continental
Stock Transfer & Trust Company, as Warrant Agent, and are subject to the terms and provisions contained therein, all of which
terms and provisions the holder of this certificate consents to by acceptance hereof. Copies of the Warrant Agreement are on file
at the office of the Warrant Agent at One State Street, 30th Floor, New York, New York 10004, and are available to any Warrant
holder on written request and without cost.


 


Upon the consummation of the Business Combination,
the Units represented by this certificate will automatically separate into the Class A Ordinary Shares and Warrants comprising
such Units.




     


     


    



This certificate is not valid unless countersigned
by the Transfer Agent and registered by the Registrar of the Company.


 


This certificate shall be governed by and
construed in accordance with the laws of the State of New York.


 


Witness the facsimile signature of its duly
authorized officers.


 


	
	 	

	[TITLE]	 	[TITLE]






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GP-Act III Acquisition Corp.


 


The Company will furnish without charge
to each unitholder who so requests, a statement of the powers, designations, preferences and relative, participating, optional
or other special rights of each class of shares or series thereof of the Company and the qualifications, limitations, or restrictions
of such preferences and/or rights.


 


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	UNIF GIFT MIN ACT —	________Custodian

________
	TEN ENT	— as tenants by the entireties	 	(Cust)

(Minor)

under Uniform Gifts to Minors
	 	 	 	 
	JT TEN	— as joint tenants with right of survivorship and not as tenants in common	 	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)



 


___  Units represented by
the within Certificate, and does hereby irrevocably constitute and appoint                                                  
Attorney to transfer the said Units on the register of members of the within named Company with full power of substitution in
the premises.


 


Dated:                                   







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	 	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) 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 UNDER THE SECURITIES EXCHANGE ACT OF 1934, AS AMENDED). 	 


 


In each case, as more fully described in the Company’s
final prospectus dated March [•], 2021, the holder(s) of this certificate shall be entitled to receive a pro rata portion
of certain funds held in the trust account established in connection with its initial public offering only in the event that (i)
the Company redeems the Class A Ordinary Shares sold in its initial public offering and liquidates because it does not consummate
an initial business combination by March [•], 2023 or by such later date approved by the Company’s shareholders in
accordance with the Company’s amended and restated memorandum and articles of association, (ii) the Company redeems the Class
A Ordinary Shares sold in its initial public offering in connection with a shareholder vote to amend the Company’s amended
and restated memorandum and articles of association (A) to modify the substance or timing of the Company’s obligation to
allow redemption in connection with the Company’s initial business combination or to redeem 100% of the Class A Ordinary
Shares if it does not complete its initial business combination by March [•], 2023 or by such later date approved by the
Company’s shareholders in accordance with the Company’s amended and restated memorandum and articles of association,
or (B) with respect to any other provision relating to the holder(s)’(s) rights or pre-initial business combination activity,
or (iii) if the holder(s) seek(s) to redeem for cash his, her, its or their respective Class A Ordinary Shares in connection with
a tender offer (or proxy solicitation, solely in the event the Company seeks shareholder approval of the proposed initial business
combination) setting forth the details of a proposed initial business combination. In no other circumstances shall the holder(s)
have any right or interest of any kind to or in the trust account.





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