SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person* FirstMark Horizon Sponsor LLC (Last) (First) (Middle) 100 5TH AVE, 3RD FLOOR (Street) NEW YORK, NY 10011 (City) (State) (Zip)	2. Date of Event Requiring Statement (Month/Day/Year) 10/05/2020	3. Issuer Name and Ticker or Trading Symbol FirstMark Horizon Acquisition Corp. [ FMAC ]
		4. Relationship of Reporting Person(s) to Issuer (Check all applicable) X Director X 10% Owner Officer (give title below) Other (specify below)	5. If Amendment, Date of Original Filed (Month/Day/Year)
			6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Class B common stock	(1)	(1)	Class A common stock	8,505,000	(1)	D(2)

1. Name and Address of Reporting Person* FirstMark Horizon Sponsor LLC (Last) (First) (Middle) 100 5TH AVE, 3RD FLOOR (Street) NEW YORK, NY 10011 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer X Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* HEITZMANN RICHARD R (Last) (First) (Middle) C/O FIRSTMARK HORIZON ACQUISITION CORP. 100 5TH AVE, 3RD FLOOR (Street) NEW YORK, NY 10011 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer X Director 10% Owner X Officer (give title below) Other (specify below) CEO

1. Name and Address of Reporting Person* JANI AMISH A (Last) (First) (Middle) C/O FIRSTMARK HORIZON ACQUISITION CORP. 100 5TH AVE, 3RD FLOOR (Street) NEW YORK, NY 10011 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer X Director 10% Owner X Officer (give title below) Other (specify below) President

Explanation of Responses:

1. As described in the issuer's registration statement on Form S-1 (File No. 333-248916) under the heading "Description of Securities--Founder Shares," the shares of Class B common stock, par value $0.0001 per share, of the issuer will automatically convert into shares of Class A common stock, par value $0.0001 per share, of the issuer at the time of the issuer's initial business combination, or earlier at the option of the holder, on a one-for-one basis, subject to certain adjustment, and have no expiration date. Includes 1,125,000 shares of Class B common stock that are subject to forfeiture if the underwriter of the issuer's initial public offering does not exercise in full its option to purchase additional units.

2. The reporting owner, FirstMark Horizon Sponsor LLC (the "Sponsor"), in whose name the securities reported herein are held, is managed by its managers, Richard Heitzmann and Amish Jani. Messrs. Heitzmann and Jani may be deemed to beneficially own shares held by the Sponsor by virtue of their shared control over the Sponsor. Each of Messrs. Heitzmann and Jani disclaims beneficial ownership of the shares held by the Sponsor, except to the extent of such person's pecuniary interest therein.

Remarks:

Exhibit 24.1 - Powers of Attorney. Messrs. Heitzmann and Jani, the managers of the Sponsor, serve on the board of directors of the issuer. For the purposes of Section 16 of the Securities Exchange Act of 1934, as amended, the Sponsor may be deemed a director by deputization with respect to the issuer on the basis of the service of Messrs. Heitzmann and Jani on the issuer's board of directors.

	/s/ FirstMark Horizon Sponsor LLC	10/05/2020
	/s/ Richard Heitzmann	10/05/2020
	/s/ Amish Jani	10/05/2020
	** Signature of Reporting Person	Date
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