Exhibit 4.2


 


SPECIMEN CLASS A ORDINARY SHARE CERTIFICATE


 


	NUMBER	 	SHARES


 


ONYX ACQUISITION CO. I

INCORPORATED UNDER THE LAWS OF THE CAYMAN ISLANDS

CLASS A ORDINARY SHARES


 


SEE REVERSE FOR


CERTAIN DEFINITIONS


CUSIP [           ]


This Certifies that                                
is the owner of                            


 


FULLY PAID AND NON-ASSESSABLE CLASS A ORDINARY
SHARES OF THE PAR VALUE OF US$0.0001 EACH OF ONYX ACQUISITION CO. I (THE “COMPANY”)


 


Subject to the Company’s amended and restated
memorandum and articles of association, as the same may be amended from time to time, and transferable on the books of the Company in
person or by duly authorized attorney upon surrender of this certificate properly endorsed.


 


The Company will be forced to redeem all of
its Class A ordinary shares if it is unable to complete a business combination within the period set forth in the Company’s amended
and restated memorandum and articles of association, as the same may be amended from time to time, all as more fully described in the
Company’s final prospectus dated              , 2021.


 


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


 


Witness the facsimile signatures of its duly
authorized officers.


 


Dated: _____________


 	Chief Executive Officer	 	Chief Financial Officer
	 	 	 




 



     


     


    

 


ONYX ACQUISITION CO. I


 


The Company will furnish without charge to each shareholder who so
requests 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. This certificate
and the shares represented thereby are issued and shall be held subject to all the provisions of the Company’s amended and restated
memorandum and articles of association, as the same may be amended from time to time, and resolutions of the Board of Directors providing
for the issue of Class A ordinary shares (copies of which may be obtained from the secretary of the Company), to all of which the holder
of this certificate by acceptance hereof assents.


 


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)
	JT TEN	—	As joint tenants with right of survivorship and not as tenants in common	 	Under Uniform Gifts to Minors Act
	 	 	 	 	_____________________________________

(State)



 


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


 


For value received, ________________________ hereby sells,
assigns and transfers unto


 


 





 



(PLEASE INSERT SOCIAL SECURITY OR OTHER IDENTIFYING
NUMBER(S) OF ASSIGNEE(S))


 


 





 



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


 


 





 



Shares represented by the within Certificate, and
does hereby irrevocably constitute and appoint


 


 





 



Attorney to transfer the said shares on the books
of the within named Company with full power of substitution in the premises.


 


Dated:__________


 


	 	 	 
		 	Shareholder






 


NOTICE: THE SIGNATURE(S) 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:



 


 





 



 


 





 



 






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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 OR ANY SUCCESSOR RULE).


 


In each case, as more fully described in the Company’s final
prospectus dated                  , 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 within the period of time set forth in the Company’s
amended and restated memorandum and articles of association, as the same may be amended from time to time, (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) that would modify the substance or timing of the Company’s obligation to
provide holders of the Class A ordinary shares the right to have their shares redeemed in connection with the Company’s initial
business combination or to redeem 100% of the Class A ordinary shares if the Company does not complete its initial business combination
within the time period set forth therein or (B) with respect to any other provision relating to the rights of holders of the Class A ordinary
shares, or (iii) if the holder(s) seek(s) to redeem for cash his, her or its 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 in or to the trust account.


 


 


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