Exhibit 4.1

NUMBER	UNITS
U-

SEE REVERSE FOR CERTAIN DEFINITIONS

CUSIP 623006 202

Mount Rainier Acquisition Corp.

UNITS CONSISTING OF ONE SHARE OF COMMON STOCK AND ONE WARRANT TO PURCHASE THREE-FOURTHS OF ONE SHARE OF COMMON STOCK

THIS CERTIFIES THAT                      is the owner of          Units.

Each Unit (“Unit”) consists of one (1) share of common stock, par value $0.0001 per share (“Common Stock”), of Mount Rainier Acquisition Corp., a Delaware corporation (the “Company”), and one redeemable warrant (the “Warrant”). Each Warrant entitles the holder thereof to purchase three-fourths (3/4) of one (1) share of Common Stock at a price of $11.50 per share (subject to adjustment). Only whole Warrants are exercisable. Each whole Warrant will become exercisable on the later of (i) thirty (30) days after the Company’s completion of a merger, capital stock exchange, asset acquisition, stock purchase, reorganization or other similar business combination with one or more businesses (each a “Business Combination”), or (ii) twelve (12) months from the closing of the Company’s initial public offering, and, unless exercised earlier, will expire at 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 thereof or Company’s liquidation. The Common Stock and Warrants comprising the Units represented by this certificate are not transferable separately prior to [•], 2021, unless A.G.P./Alliance Global Partners 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 the Company’s initial public offering and the Company issuing a press release announcing when separate trading will begin. The terms of the Warrants are governed by a Warrant Agreement, dated as of [•], 2021, between the Company and American 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 6201 15th Avenue Brooklyn, NY 11219, and are available to any Warrant holder on written request and without cost.

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

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

Witness the facsimile signature of a duly authorized signatory of the Company.

Authorized Signatory Transfer Agent and Registrar

Mount Rainier 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 stock 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)
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 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 do hereby irrevocably constitute and appoint

Attorney to transfer the said Units on the books of the within named Company 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) 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 the Company’s initial public offering only in the event that (i) the Company redeems the shares of Common Stock sold in the Company’s initial public offering and liquidates because it does not consummate an initial business combination by [•], 2023 (or such later date as the Company’s amended and restated certificate of incorporation may be amended to provide for), (ii) the Company offers to redeem the shares of Common Stock sold in its initial public offering in connection with a stockholder vote to amend the Company’s amended and restated certificate of incorporation (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 certain amendments to the Company’s certificate of incorporation prior thereto or to redeem 100% of such Common Stock if it does not consummate an initial business combination by [•], 2023 or (B) with respect to any other provision relating to stockholders’ rights or pre-initial business combination activity, and the holder(s) of this certificate elects to have the shares of Common Stock held by him, her or it redeemed pursuant to that offer, or (iii) if the holder(s) seek(s) to redeem for cash his, her or its respective shares of Common Stock in connection with a tender offer (or proxy solicitation, solely in the event the Company seeks stockholder 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.