Sec Form 3 Filing - RMG Sponsor III, LLC @ RMG Acquisition Corp. III - 2021-02-04

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person RMG Sponsor III, LLC 2. Issuer Name and Ticker or Trading Symbol RMG Acquisition Corp. III [ RMGC] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O RMG ACQUISITION CORP. III, 50 WEST STREET, SUITE 40C 3. Date of Earliest Transaction (MM/DD/YY) 02/04/2021 (Street) NEW YORK, NY10006 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Class B Common Stock ( 1 ) ( 1 ) ( 1 ) Class A Common Stock 12,075,000 I See footnote ( 2 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other RMG Sponsor III, LLC C/O RMG ACQUISITION CORP. III 50 WEST STREET, SUITE 40C NEW YORK, NY10006 X MKC Investments LLC C/O RMG ACQUISITION CORP. 50 WEST STREET, SUITE 40C NEW YORK, NY10006 X X Carpenter David James C/O RMG ACQUISITION CORP. 50 WEST STREET, SUITE 40C NEW YORK, NY10006 X X Mancini Robert S. C/O RMG ACQUISITION CORP. 50 WEST STREET, SUITE 40C NEW YORK, NY10006 X X Chief Executive Officer KASSIN PHILIP C/O RMG ACQUISITION CORP. III, 50 WEST STREET, SUITE 40C NEW YORK, NY10006 X X President, COO Signatures RMG Sponsor III, LLC By: MKC Investments LLC, its sole managing member By: /s/ Wesley Sima, Attorney-in-fact for Philip Kassin, President and Chief Operating Officer 02/04/2021 Signature of Reporting Person Date MKC Investments LLC By: /s/ Wesley Sima, Attorney-in-fact for Philip Kassin, President and Chief Operating Officer 02/04/2021 Signature of Reporting Person Date /s/ Wesley Sima, Attorney-in-fact for David James Carpenter 02/04/2021 Signature of Reporting Person Date /s/ Wesley Sima, Attorney-in-fact for Robert S. Mancini 02/04/2021 Signature of Reporting Person Date /s/ Wesley Sima, Attorney-in-fact for Philip Kassin 02/04/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The Class B common stock is convertible into shares of Class A common stock on a one-for-one basis, subject to adjustment, at the option of the holder and will automatically convert into shares of Class A common stock at the completion of the Issuer's initial business combination. ( 2 )RMG Sponsor III, LLC ("Sponsor") is the record holder of the shares reported herein. MKC Investments LLC is the sole managing member of Sponsor, and Messrs. Carpenter, Mancini and Kassin are the managing members of MKC Investments LLC. As such, each of Messrs. Carpenter, Mancini and Kassin may be deemed to share beneficial ownership of the Class B common stock held directly by Sponsor. Each such individual disclaims any beneficial ownership of such shares other than to the extent of his pecuniary interest therein, if any.

Remarks: Exhibit 24.1 - Power of Attorney Exhibit 24.2 - Power of Attorney Exhibit 24.3 - Power of Attorney

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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