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 13, 2016

AK STEEL HOLDING CORPORATION

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (513) 425-5000

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:

On June 13, 2016, AK Steel Holding Corporation (the “Company”) issued a press release announcing that AK Steel Corporation, its wholly-owned subsidiary (“AK Steel”), commenced an offer to purchase (the “Tender Offer”) for cash any and all of the $380 million outstanding principal amount of its 8.75% senior secured notes due 2018 (CUSIPs U00974 AB8 and 001546 AQ3) (the “Notes”). The Tender Offer is being made upon the terms and subject to the conditions set forth in the Offer to Purchase dated June 13, 2016, and a related Letter of Transmittal and Notice of Guaranteed Delivery, which set forth the terms and conditions of the Tender Offer in full detail. Holders who validly tender their Notes at or prior to 5:00 p.m. New York City time on June 17, 2016 (the “Expiration Date”) will be eligible to receive the purchase price of $1,047.50 per $1,000 principal amount of Notes tendered. Tendering holders will also receive accrued and unpaid interest from the last applicable interest payment date to, but not including, the settlement date of the Tender Offer.

AK Steel expressly reserves the right, in its sole discretion, subject to applicable law, to terminate the Tender Offer at any time prior to the Expiration Date. The Tender Offer is subject to the satisfaction of certain conditions set forth in the Offer to Purchase.

A copy of the Company’s press release is attached as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated into this Item 8.01 by reference.

2

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.

3