UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): November 6, 2025

Dynamix Corporation III

(Exact name of registrant as specified in its charter)

1980 Post Oak Blvd., Suite 100

PMB 6373

Houston, TX 77056

(Address of principal executive offices, including zip code)

Registrant’s telephone number, including area code: (646) 792 5600

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

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

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 1.01. Entry into a Material Definitive Agreement.

On October 31, 2025, Dynamix Corporation III (the “Company”) consummated its initial public offering (“IPO”) of 20,125,000 units (the “Units”), including the issuance of 2,625,000 Units as a result of the underwriters’ full exercise of their option to purchase additional Units. Each Unit consists of one Class A ordinary share of the Company, par value $0.0001 per share (the “Class A Ordinary Shares”), and one-half of one redeemable warrant of the Company (each, a “Warrant”), with each whole Warrant entitling the holder thereof to purchase one Class A Ordinary Share for $11.50 per share. The Units were sold at a price of $10.00 per Unit, generating gross proceeds to the Company of $201,250,000 (before underwriting discounts and commissions and offering expenses).

Simultaneously with the closing of the IPO, pursuant to (i) the Private Placement Warrants Purchase Agreement between the Company and DynamixCore Holdings III, LLC (the “Sponsor”), dated October 29, 2025, and (ii) the Private Placement Warrants Purchase Agreement by and among the Company, Cohen & Company Capital Markets, a division of Cohen & Company Securities, LLC, and Clear Street LLC (collectively, the “Subscriber”), dated October 29, 2025, the Company completed the private sale of 4,262,500 warrants to the Sponsor and 2,012,500 warrants to the Subscriber, respectively (the “Private Placement”), at a purchase price of $1.00 per Warrant (collectively, the “Private Placement Warrants”), generating gross proceeds to the Company of $6,275,000.

On October 31, 2025, an amount of $201,250,000 ($10.00 per Unit) from the net proceeds of the sale of the Units and the sale of the Private Placement Warrants, was placed in a U.S.-based trust account at J.P. Morgan Chase Bank, N.A., maintained by Odyssey Transfer and Trust Company, acting as trustee.

An audited balance sheet as of October 31, 2025, reflecting receipt of the proceeds upon consummation of the IPO and the Private Placement, has been issued by the Company and is included as Exhibit 99.1 to this Current Report on Form 8-K.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits

The following exhibits are being filed herewith:

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.