UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-A

FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES

PURSUANT TO SECTION 12(b) OR 12(g) OF THE

SECURITIES EXCHANGE ACT OF 1934

Dynamix Corporation III

(Exact name of registrant as specified in its charter)

Cayman Islands	00-0000000
(State of incorporation or organization)	(I.R.S. Employer Identification No.)
1980 Post Oak Blvd., Suite 100 PMB 6373 Houston, TX	77056
(Address of principal executive offices)	(Zip Code)

Securities to be registered pursuant to Section 12(b) of the Act:

Title for each class to be so registered	Name of each exchange on which each class is to be registered
Units, each consisting of one Class A ordinary share, par value $0.0001 per share, and one-half of one redeemable warrant	The Nasdaq Stock Market LLC
Class A ordinary shares, par value $0.0001 per share	The Nasdaq Stock Market LLC
Redeemable warrants, each whole warrant exercisable for one Class A ordinary share, par value $0.0001 per share, at an exercise price of $11.50 per share	The Nasdaq Stock Market LLC

If this form relates to the registration of a class of securities pursuant to Section 12(b) of the Exchange Act and is effective pursuant to General Instruction A.(c) or (e), check the following box. ☒

If this form relates to the registration of a class of securities pursuant to Section 12(g) of the Exchange Act and is effective pursuant to General Instruction A.(d) or (e), check the following box. ☐

If this form relates to the registration of a class of securities concurrently with a Regulation A offering, check the following box.  ☐

Securities Act registration statement file number to which this form relates (if applicable): 333-289517

Securities to be registered pursuant to Section 12(g) of the Act: N/A

Item 1. Description of Registrant’s Securities to be Registered.

The securities to be registered hereby are the units, each consisting of one Class A ordinary share, $0.0001 par value per share (“Class A ordinary shares”), and one-half of one redeemable warrant, Class A ordinary shares and redeemable warrants to purchase Class A ordinary shares, of Dynamix Corporation III (the “Registrant”). The description of the units, Class A ordinary shares and redeemable warrants set forth under the heading “Description of Securities” in the Registrant’s prospectus forming a part of its Registration Statement on Form S-1 (File No. 333-289517), originally filed with the U.S. Securities and Exchange Commission on August 12, 2025, as thereafter amended and supplemented from time to time (the “Registration Statement”), to which this Form 8-A relates is incorporated by reference herein. Any form of prospectus or prospectus supplement to the Registration Statement that includes such descriptions and that are subsequently filed are hereby also incorporated by reference herein.

Item 2. Exhibits.

Pursuant to the Instructions as to Exhibits with respect to Form 8-A, no exhibits are required to be filed as part of this registration statement because no other securities of the Registrant are registered on The Nasdaq Stock Market LLC and the securities registered hereby are not being registered pursuant to Section 12(g) of the Securities Exchange Act of 1934, as amended.

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SIGNATURE

Pursuant to the requirements of Section 12 of the Securities Exchange Act of 1934, the Registrant has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized.

Date: October 28, 2025

Dynamix Corporation III
By:	/s/ Andrea Bernatova
	Name:	Andrea Bernatova
	Title:	Chief Executive Officer

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