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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): June 23, 2026

SOLUNA HOLDINGS, INC.

(Exact name of Registrant as Specified in Its Charter)

Nevada |  | 001-40261 |  | 14-1462255
(State or Other Jurisdiction of Incorporation) |  | (Commission File Number) |  | (IRS Employer Identification No.)

325 Washington Avenue Extension |  |
Albany, New York |  | 12205
(Address of Principal Executive Offices) |  | (Zip Code)

Registrant’s Telephone Number, Including Area Code: (516) 216-9257

N/A

(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:

☐ | Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
☐ | Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)
☐ | Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))
☐ | Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

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

Title of each class |  | Trading Symbol(s) |  | Name of each exchange on which registered
Common stock, par value $0.001 per share |  | SLNH |  | The Nasdaq Stock Market LLC
9.0% Series A Cumulative Perpetual Preferred Stock, par value $0.001 per share |  | SLNHP |  | The Nasdaq Stock Market LLC

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 5.03 Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year.

Soluna Holdings, Inc. (the “Company”) previously designated 187,500 shares of preferred stock as Series B Convertible Preferred Stock (the “Preferred Stock”). In 2026, the previously issued and outstanding 62,500 shares of Preferred Stock were converted, in their entirety, to 6,510,416 shares of common stock of the Company. Accrued dividends of $2.1 million were paid upon the full conversion of such shares of Preferred Stock.

On June 23, 2026, the Company filed a Withdrawal of Designation relating to the Preferred Stock (the “Withdrawal of Designation”) with the Secretary of State of the State of Nevada and terminated the designation of the Preferred Stock. At the time of the filing of the Withdrawal of Designation, no shares of Preferred Stock were outstanding. The Withdrawal of Designation was effective upon filing and eliminated from the Company’s Articles of Incorporation, as amended, all matters set forth in the previously-filed Certificate of Designation with respect to the previously designated Preferred Stock.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

Exhibit No. |  | Description
3.1 |  | Certificate, Amendment or Withdrawal of Designation, relating to the Series B Convertible Preferred Stock, filed with the Secretary of State of Nevada on June 23, 2026.
104 |  | Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURES

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

| SOLUNA HOLDINGS, INC.
Date: June 25, 2026 | By: | /s/ Michael Picchi
|  | Michael Picchi
|  | Chief Financial Officer
|  | (principal financial officer)