Rithm Acquisition Sponsor reports 6,335,000 shares (21.5%) stake

Rithm Acquisition Corp. (RAC) disclosed a Schedule 13G reporting beneficial ownership of 6,335,000 ordinary shares, equal to 21.5% of Class A and Class B shares outstanding as of September 30, 2025.

Rhea-AI Filing Summary

Rithm Acquisition Corp. (RAC) disclosed a Schedule 13G reporting beneficial ownership of 6,335,000 ordinary shares, equal to 21.5% of Class A and Class B shares outstanding as of September 30, 2025.

The stake is held of record by Rithm Acquisition Corp Sponsor LLC and consists of 5,675,000 Class B founder shares and 660,000 Class A shares included in private placement units. The Class B shares automatically convert into Class A on a one‑for‑one basis at the time of the initial business combination, subject to adjustment. The Sponsor has sole voting and dispositive power over these shares, while Rithm Capital Corp. and Michael Nierenberg are reported to share voting and dispositive power through their control relationships and each disclaims beneficial ownership except to the extent of pecuniary interest.

Insights

Equity ownership analyst

RAC’s sponsor reports a 21.5% beneficial stake via founder and private placement shares.

Rithm Acquisition Corp Sponsor LLC is the record holder of 6,335,000 ordinary shares as of September 30, 2025, representing 21.5% of Class A and Class B outstanding. The position includes 5,675,000 Class B founder shares and 660,000 Class A from private placement units.

The filing notes the Class B shares convert 1:1 into Class A at the initial business combination, subject to adjustment. The Sponsor reports sole voting/dispositive power, while Rithm Capital Corp. and Michael Nierenberg report shared power through control relationships and disclaim beneficial ownership beyond pecuniary interests.

This is typical for SPAC structures and primarily informational. Actual impact depends on future business combination outcomes and any subsequent ownership changes disclosed in later filings.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What stake did RAC’s sponsor report in this Schedule 13G for RAC?

The filing reports 6,335,000 ordinary shares, representing 21.5% of Class A and Class B shares outstanding as of September 30, 2025.

How is the 6,335,000-share position in RAC composed?

It includes 5,675,000 Class B founder shares and 660,000 Class A shares included in private placement units.

When and how do RAC’s Class B founder shares convert?

The Class B shares automatically convert into Class A on a one-for-one basis at the time of the initial business combination, subject to adjustment.

Who holds voting and dispositive power over the reported RAC shares?

Rithm Acquisition Corp Sponsor LLC reports sole voting and dispositive power. Rithm Capital Corp. and Michael Nierenberg report shared power via control relationships.

What is the date tied to RAC’s ownership figures in the filing?

The ownership percentages and share counts are stated as of September 30, 2025.

Which entities and individuals are named as reporting persons in the RAC 13G?

Rithm Acquisition Corp Sponsor LLC, Rithm Capital Corp., and Michael Nierenberg are the reporting persons.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 11/05/2025 - 05:19 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Rithm Acquisition Corp.

(Name of Issuer)

Class A Ordinary Shares, par value $0.0001 per share

(Title of Class of Securities)

G75751100

(CUSIP Number)

09/30/2025

(Date of Event Which Requires Filing of this Statement)

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

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No. G75751100

1

Names of Reporting Persons

Rithm Acquisition Corp Sponsor LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 6,335,000.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 6,335,000.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

6,335,000.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

21.5 %

12

Type of Reporting Person (See Instructions)

PN

Comment for Type of Reporting Person: Row 5, 7, 9, and 11: See Item 4 below. Rithm Acquisition Corp Sponsor LLC holds 5,675,000 Class B ordinary shares of the Issuer, which are automatically convertible into the Issuer's Class A ordinary shares, and 660,000 Class A ordinary shares included in the private placement units, in each case as more fully described under the heading "Description of Securities" in the Issuer's registration statement on Form S-1 (File No. 333-284671).

SCHEDULE 13G

CUSIP No. G75751100

1

Names of Reporting Persons

Rithm Capital Corp.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 6,335,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 6,335,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

6,335,000.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

21.5 %

12

Type of Reporting Person (See Instructions)

PN

Comment for Type of Reporting Person: Row 6, 8, 9, and 11: See Item 4 below. Rithm Acquisition Corp Sponsor LLC holds 5,675,000 Class B ordinary shares of the Issuer, which are automatically convertible into the Issuer's Class A ordinary shares, and 660,000 Class A ordinary shares included in the private placement units, in each case as more fully described under the heading "Description of Securities" in the Issuer's registration statement on Form S-1 (File No. 333-284671).

SCHEDULE 13G

CUSIP No. G75751100

1

Names of Reporting Persons

Michael Nierenberg

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 6,335,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 6,335,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

6,335,000.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

21.5 %

12

Type of Reporting Person (See Instructions)

PN

Comment for Type of Reporting Person: Row 6, 8, 9, and 11: See Item 4 below. Rithm Acquisition Corp Sponsor LLC holds 5,675,000 Class B ordinary shares of the Issuer, which are automatically convertible into the Issuer's Class A ordinary shares, and 660,000 Class A ordinary shares included in the private placement units, in each case as more fully described under the heading "Description of Securities" in the Issuer's registration statement on Form S-1 (File No. 333-284671).

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Rithm Acquisition Corp.
(b)	Address of issuer's principal executive offices: 799 Broadway, 8th Floor, New York, NY 10003
Item 2.
(a)	Name of person filing: Rithm Acquisition Sponsor LLC Rithm Capital Corp.
(b)	Address or principal business office or, if none, residence: c/o Rithm Acquisition Corp. 799 Broadway, 8th Floor New York, New York 10003
(c)	Citizenship: The citizenship of Rithm Acquisition Sponsor LLC is Delaware. The citizenship of Rithm Capital Corp. is Delaware. The citizenship of Michael Nierenberg is the United States.
(d)	Title of class of securities: Class A Ordinary Shares, par value $0.0001 per share
(e)	CUSIP No.: G75751100
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: The responses to Items 5-11 of the cover pages of this Schedule 13G are incorporated herein by reference. As of September 30, 2025, the Reporting Persons may be deemed to beneficially own 6,335,000 shares of the Issuer's Class A and Class B ordinary shares, representing 21.5% of the total shares of Class A and Class B ordinary shares issued and outstanding. The Class B ordinary shares are automatically convertible into the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment, as more fully described under the heading "Description of Securities - Founder Shares" in the Issuer's registration statement on Form S-1 (File No. 333-284671). Rithm Acquisition Sponsor LLC is the record holder of such ordinary shares, and Rithm Acquisition Sponsor LLC is controlled by Rithm Capital Corp., an affiliate of the Issuer, and Michael Nierenberg as a result of his role as chief executive officer, chairman of the board and president of Rithm Capital Corp. As a result, each of Rithm Acquisition Sponsor LLC, Rithm Capital Corp. and Mr. Nierenberg may be deemed to have beneficial ownership of the Class A and Class B ordinary shares held by Rithm Acquisition Sponsor LLC, but each disclaims such beneficial ownership except to the extent of such person's or entity's pecuniary interest therein.
(b)	Percent of class: See responses to Item 11 on each cover page.
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: See responses to Item 5 on each cover page.
	(ii) Shared power to vote or to direct the vote: See responses to Item 6 on each cover page.
	(iii) Sole power to dispose or to direct the disposition of: See responses to Item 7 on each cover page.
	(iv) Shared power to dispose or to direct the disposition of: See responses to Item 8 on each cover page.
Item 5.	Ownership of 5 Percent or Less of a Class.
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.	Certifications:
	Not Applicable

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.

Rithm Acquisition Corp Sponsor LLC

Signature:	/s/ Nicola Santoro
Name/Title:	Nicola Santoro, Chief Financial Officer of Rithm Acquisition Sponsor LLC
Date:	11/05/2025

Rithm Capital Corp.

Signature:	/s/ Nicola Santoro
Name/Title:	Nicola Santoro, Chief Financial Officer of Rithm Capital Corp.
Date:	11/05/2025

Michael Nierenberg

Signature:	/s/ Michael Nierenberg
Name/Title:	Michael Nierenberg
Date:	11/05/2025