SCHEDULE 13G

(Amendment No.   )*

Spartan Acquisition Corp. III

(Name of Issuer)

Class A Common Stock, par value $0.0001 per
share

(Title of Class of Securities)

84677R106

(CUSIP Number)

December 31, 2021

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

^* The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

Spartan Acquisition Corp. III

9 West 57th Street, 43rd Floor

New York, NY 10019

This statement is filed by (i) Spartan Acquisition Sponsor III LLC (“Spartan III Sponsor”); (ii) AP Spartan Energy Holdings III, L.P. (“AP Spartan”); (iii) Apollo ANRP Advisors III, L.P. (“ANRP Advisors”); (iv) Apollo ANRP Capital Management III, LLC (“ANRP Capital Management”); (v) APH Holdings, L.P. (“APH Holdings”); and (vi) Apollo Principal Holdings III GP, Ltd. (“Principal Holdings III GP”). The foregoing are collectively referred to herein as the “Reporting Persons.”

Spartan III Sponsor holds shares of Class B Common Stock of the Issuer convertible into Class A Common Stock.

AP Spartan is the sole member of Spartan III Sponsor. ANRP Advisors is the general partner of AP Spartan. ANRP Capital Management is the general partner of ANRP Advisors. APH Holdings is the sole member of ANRP Capital Management. Principal Holdings III GP is the general partner of APH Holdings.

The address of the principal business office of each of Spartan III Sponsor and AP Spartan is 9 West 57th Street, 43rd Floor, New York, New York 10019. The address of the principal business office of each of ANRP Advisors and Principal Holdings III GP is c/o Walkers Corporate Limited; Cayman Corporate Centre; 27 Hospital Road; George Town; Grand Cayman KY1-9008. The address of the principal business office of each of ANRP Capital Management and APH Holdings is One Manhattanville Road, Suite 201, Purchase, New York, 10577.

Spartan III Sponsor is a Delaware limited liability company. AP Spartan is a Delaware limited partnership. ANRP Advisors and APH Holdings are each exempted limited partnerships registered in the Cayman Islands. ANRP Capital Management and Principal Holdings III GP are each an exempted company registered in the Cayman Islands with limited liability.

Class A Common Stock, par value $0.0001 per share (the “Common Stock”).

84677R106

Not applicable.

Beneficial ownership information is reported as of the date of filing of this Schedule 13G.

AP Spartan, ANRP Advisors, ANRP Capital Management, APH Holdings, and Principal Holdings III GP, and Messrs. Scott Kleinman, Marc Rowan and James Zelter, the directors of Principal Holdings III GP, each disclaim beneficial ownership of all shares of Common Stock included in this filing, and the filing of this report shall not be construed as an admission that any such person or entity is the beneficial owner of any such securities for purposes of Section 13(d) or 13(g) of the Securities Exchange Act of 1934, as amended, or for any other purpose.

The percentages are based on 55,200,000 shares of Common Stock outstanding as of November 10, 2021, as disclosed in the Issuer’s Quarterly Report on Form 10-Q filed on November 26, 2021.

0 for all Reporting Persons

0 for all Reporting Persons

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following: ¨

Not applicable.

Not applicable.

Not applicable.

Not applicable.

Not applicable.

[The remainder of this page is intentionally left blank.]

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Date: February 11, 2022