UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 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 12, 2013

CLEARWIRE CORPORATION

(Exact Name of Registrant as Specified in its Charter)

1475 120th Avenue Northeast, Bellevue, Washington 98005

(Address of Principal Executive Offices) (Zip Code)

(425) 216-7600

(Registrant’s Telephone Number, Including Area Code)

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 (see General Instruction A.2. below):

The Company hereby furnishes the information in Exhibit 99.1 hereto, a press release dated June 12, 2013 and in Exhibit 99.2 hereto, an email communication to Clearwire employees by Erik Prusch, President and Chief Executive Officer, on June 12, 2013.

(d) Exhibits.

Cautionary Statement Regarding Forward-Looking Statements

This document includes “forward-looking statements” within the meaning of the securities laws. The words “may,” “could,” “should,” “estimate,” “project,” “forecast,” “intend,” “expect,” “anticipate,” “believe,” “target,” “plan,” “providing guidance” and similar expressions are intended to identify information that is not historical in nature.

This document contains forward-looking statements relating to the proposed merger and related transactions (the “transaction”) between Sprint and Clearwire. All statements, other than historical facts, including statements regarding the expected timing of the closing of the transaction; the ability of the parties to complete the transaction considering the various closing conditions; the expected benefits and efficiencies of the transaction; the competitive ability and position of Sprint and Clearwire; and any assumptions underlying any of the foregoing, are forward- looking statements. Such statements are based upon current plans, estimates and expectations that are subject to risks, uncertainties and assumptions. The inclusion of such statements should not be regarded as a representation that such plans, estimates or expectations will be achieved. You should not place undue reliance on such statements. Important factors that could cause actual results to differ materially from such plans, estimates or expectations include, among others, any conditions imposed in connection with the transaction, approval of the transaction by Clearwire stockholders, the satisfaction of various other conditions to the closing of the transaction contemplated by the merger agreement, and other factors discussed in Clearwire’s and Sprint’s Annual Reports on Form 10-K for their respective fiscal years ended December 31, 2012, their other respective filings with the U.S. Securities and Exchange Commission (the “SEC”) and the proxy statement and other materials that have been or will be filed with the SEC by Clearwire in connection with the transaction. There can be no assurance that the transaction will be completed, or if it is completed, that it will close within the anticipated time period or that the expected benefits of the transaction will be realized.

Clearwire does not undertake any obligation to update any forward-looking statement to reflect events or circumstances after the date on which the statement is made or to reflect the occurrence of unanticipated events. Readers are cautioned not to place undue reliance on any of these forward-looking statements.

Additional Information and Where to Find It

The tender offer described in this document has commenced, but this document and the description contained herein is neither an offer to purchase nor a solicitation of an offer to sell shares of Clearwire. DISH has filed on June 12, 2013 a revised tender offer statement on Schedule TO with the SEC and Clearwire will file on June 12, 2013 a solicitation/recommendation on Schedule 14D-9 with respect to the tender offer. The offer to purchase shares of Clearwire common stock will only be made pursuant to the offer to purchase, the letter of transmittal and related documents filed with such Schedule TO. The tender offer statement (including an offer to purchase, a related letter of transmittal and other offer documents) and the solicitation/recommendation statement, as each

may be amended from time to time, will contain important information that should be read carefully by Clearwire’s stockholders before any decision is made with respect to the tender offer. In connection with the transaction, Clearwire has filed a Rule 13e-3 Transaction Statement and a definitive proxy statement with the SEC. The definitive proxy statement has been mailed to the Clearwire’s stockholders. The tender offer statement and the solicitation/recommendation statement (and all other documents filed with the SEC) will be available at no charge on the SEC’s website: www.sec.gov.

Participants in the Solicitation

Clearwire and its officers and directors and Sprint and its officers and directors may be deemed to be participants in the solicitation of proxies from Clearwire stockholders with respect to the transaction. Information about Clearwire officers and directors and their ownership of Clearwire common shares is set forth in the definitive proxy statement for Clearwire’s Special Meeting of Stockholders, which was filed with the SEC on April 23, 2013. Information about Sprint officers and directors is set forth in Sprint’s Annual Report on Form 10-K for the year ended December 31, 2012, which was filed with the SEC on February 28, 2013. Investors and security holders may obtain more detailed information regarding the direct and indirect interests of the participants in the solicitation of proxies in connection with the transaction by reading the definitive proxy statement regarding the transaction, which was filed by Clearwire with the SEC.

SIGNATURES

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

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