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): December 18, 2025

Core Natural Resources, Inc.

(Exact name of registrant as specified in its charter)

Delaware	001-38147	82-1954058
(State or other jurisdiction of incorporation)	(Commission File Number)	(IRS Employer Identification No.)

275 Technology Drive Suite 101

Canonsburg, Pennsylvania 15317

(Address of principal executive offices)

(Zip code)

Registrant's telephone number, including area code:

(724) 416-8300

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, $0.01 par value	CNR	New York Stock Exchange

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))

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 7.01 Regulation FD Disclosure.

On December 18, 2025, Core Natural Resources, Inc. (the “Company”) issued a press release announcing that the Company has resumed longwall operations at its Leer South mine in West Virginia and providing an update regarding the productivity levels of its West Elk mine in Colorado. A copy of the press release is furnished as Exhibit 99.1 hereto and is incorporated herein by reference.

The information contained in this Item 7.01 and Exhibit 99.1 shall be considered “furnished” and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of that Section or Sections 11 and 12(a)(2) of the Securities Act of 1933, as amended, nor shall it be deemed incorporated by reference into any reports or filings with the Securities and Exchange Commission, whether made before or after the date hereof, except as expressly set forth by specific reference in such a filing.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

Exhibit 99.1        Press release of Core Natural Resources, Inc. dated December 18, 2025

Exhibit 104        Cover Page Interactive Data File (formatted as inline XBRL and contained in Exhibit 101)

SIGNATURES

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.

Core Natural Resources, Inc.
(Registrant)
By:	/s/ MITESHKUMAR B. THAKKAR
	Miteshkumar B. Thakkar
	Chief Financial Officer and President

Dated: December 18, 2025