Exhibit 4.1

NUMBER UNITS

U-

SEE REVERSE FOR CERTAIN

DEFINITIONS

CUSIP [•]

MOSAIC ACQUISITION CORP.

UNITS CONSISTING OF ONE CLASS A ORDINARY SHARE AND ONE-THIRD OF ONE WARRANT 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 (“Ordinary Shares”), of Mosaic Acquisition Corp., a Cayman Islands exempted company (the “Company”), and one-third (1/3) of one warrant (each whole warrant, a “Warrant”). Each whole Warrant entitles the holder to purchase one Ordinary Share (subject to adjustment) for $11.50 per share (subject to adjustment). Each 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 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 “Expiration Date”). The Ordinary Shares and Warrants comprising the Units represented by this certificate are not transferable separately prior to                 , 20    , unless Deutsche Bank Securities Inc., RBC Capital Markets, LLC and J.P. Morgan Securities LLC elect to allow earlier separate trading, 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 offering and issuing a press release announcing when separate trading will begin. The terms of the Warrants are governed by a Warrant Agreement, dated as of                 , 2017, 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 17 Battery Place, New York, New York 10004, 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 its duly authorized officers.

Secretary Chief Executive Officer

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Mosaic 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)
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 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                                                  

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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.
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).

In each case, as more fully described in the Company’s final prospectus dated                 , 2017, 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 Class A Ordinary Shares sold in its initial public offering and liquidates because it does not consummate an initial business combination by                 , 20    , (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 to modify the substance or timing of the Company’s obligation to redeem 100% of the Class A Ordinary Shares if it does not consummate an initial business combination by                 , 20    , 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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