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 30, 2011

Cloud Peak Energy Inc.

Cloud Peak Energy Resources LLC

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (307) 687-6000

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:

o            Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o            Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o            Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o            Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Antelope Coal LLC Federal Coal Lease

On June 30, 2011, Antelope Coal LLC, an indirect subsidiary of Cloud Peak Energy Inc., entered into a Federal Coal Lease (the “Lease”) with the United States of America through the Bureau of Land Management (the “BLM”) of the United States Department of the Interior for the West Antelope II North Coal Tract, which is effective on July 1, 2011.  Subject to the terms and conditions thereof, the Lease covers approximately 2,838 acres and provides Antelope Coal LLC with the exclusive right to drill for, mine, extract, remove or otherwise process and dispose of the coal deposits in, upon, or under the lands described in the Lease.  The BLM estimates the tract contains approximately 350 million tons of mineable coal.  The company bid approximately $297.7 million and has submitted a payment for approximately $59.5 million, which is the first of five equal payments for the federal coal lease.  The company is also required to pay customary production royalties and per acre annual rental payments to the BLM, and the company has agreed to indemnify the BLM from any claims arising out of the company’s activities and operations under the Lease.

The foregoing overview of the Lease does not contain all of the terms and conditions of the Lease.  For the complete terms and conditions, refer to Exhibit 10.1 of this Form 8-K, which is incorporated into this Item 1.01 by reference.

Item 1.01 of this Current Report on Form 8-K is incorporated herein by reference.

Cautionary Note Regarding Forward-Looking Statements

This Form 8-K contains “forward-looking statements” within the meaning of the safe harbor provisions of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. Forward-looking statements are not statements of historical facts and often contain words such as “may,” “will,” “expect,” “believe,” “anticipate,” “plan,” “estimate,” “seek,” “could,” “should,” “intend,” “potential,” or words of similar meaning. Forward-looking statements are based on management’s current expectations or beliefs, as well as assumptions and estimates regarding our company, industry, economic conditions, government regulations and energy policies and other factors. Forward-looking statements may include, for example, (1) our estimates of proven and probable coal reserves, future production and reserve life, (2) our ability to obtain all required regulatory permits and approvals to mine newly acquired coal tons in a timely and cost-effective manner, (3) the impact of pending or future third party litigation and regulatory challenges, (4) business development and growth initiatives; and (5) other statements regarding our plans, strategies, prospects and expectations concerning our business, operating results, financial condition and other matters that do not relate strictly to historical facts. These statements are subject to significant risks, uncertainties, and assumptions that are difficult to predict and could cause actual results to differ materially from those expressed or implied in the forward-looking statements. For a discussion of some of the factors that could adversely affect our future results, refer to the risk factors described from time to time in the reports and registration statements we file with the Securities and Exchange Commission (“SEC”), including those in Item 1A - Risk Factors in our most recent Form 10-K and any updates thereto in our Forms 10-Q and current reports on Forms 8-K. There may be other risks and uncertainties that are not currently known to us or that we currently believe are not material. We make forward-looking statements based on currently available information, and we assume no obligation to, and expressly disclaim any obligation to, update or revise publicly any forward-looking statements made in this Form 8-K, whether as a result of new information, future events or otherwise, except as required by law.

2

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.

3

EXHIBIT INDEX

4