UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of May 2018

Commission File Number: 001-36427

CHEETAH MOBILE INC.

Building No. 8

Hui Tong Times Square

Yaojiayuan South Road

Beijing 100123

People’s Republic of China

(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F  ☒            Form 40-F  ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):  ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):  ☐

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, thereunto duly authorized.

Date: May 23, 2018

Exhibit Index

Exhibit 99.1

Cheetah Mobile Announces First Quarter 2018

Unaudited Consolidated Financial Results

May 21, 2018

BEIJING, May 21, 2018 /PRNewswire/ — Cheetah Mobile Inc. (NYSE: CMCM) (“Cheetah Mobile” or the “Company”), a leading mobile internet company with strong global vision, today announced its unaudited consolidated financial results for the first quarter ended March 31, 2018.

First Quarter 2018 Financial Highlights

First Quarter 2018 Operating Metrics

Artificial Intelligence Technology

Mr. Sheng Fu, Cheetah Mobile’s Chairman and Chief Executive Officer, stated, “We began 2018 on a solid note with total revenues exceeding the high-end of our guidance. In the first quarter of 2018, our utility product business continued to generate strong profits and cash flow. We also solidified our leading position in the mobile casual game market by further enriching our game pipeline. Our artificial intelligence (“AI”) powered businesses made steady progress as well. In March, Cheetah Mobile and Beijing OrionStar jointly launched five practical and easy-to-use robotics products, which are powered by Orion OS, an open platform for robotics, which has been developed by Beijing OrionStar. Going forward, we aim to drive steady and healthy profit from our core businesses while simultaneously leveraging our extensive technology and product experience to expand our robotic product offerings.”

Mr. Vincent Jiang, Cheetah Mobile’s Chief Financial Officer, commented, “We continued to expand our profits and margins in the first quarter of 2018 as a result of our strategic efforts to optimize the cost and expense structure for our utility products business and our initiative to dispose of News Republic. Looking ahead, we will continue to drive higher operational efficiency for our core businesses, which in turn will fund our investment in AI-powered business and build long-term growth for Cheetah Mobile and its shareholders.”

First Quarter 2018 Consolidated Financial Results

REVENUES

Total revenues were RMB1,145.1 million (US$182.6 million) in the first quarter of 2018.

By platform, revenues generated from the mobile business were 88.9% of total revenues in the first quarter of 2018, up from 85.3% in the same period last year.

By region, revenues generated from the Chinese market constituted 39.1% of total revenues in the first quarter of 2018, up from 27.6% in the same period last year. The growth of the Company’s revenues in the Chinese market was attributable to a ramp-up of mobile utility products and related services businesses in China and increased mobile game revenues in the Chinese market, where the Company’s mobile games continue to gain popularity.

Revenues generated from the overseas market constituted 60.9% of total revenues in the first quarter of 2018, a 17.6% decrease year over year to RMB697.5 million (US$111.2 million), mainly due to the impact of lock screen ads. Excluding the foreign exchange impact, revenues from the overseas market decreased by 11.4% year over year.

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COST OF REVENUES AND GROSS PROFIT

Cost of revenues decreased by 14.6% year over year to RMB391.2 million (US$62.4 million) in the first quarter of 2018. The year-over-year decrease resulted from reduced bandwidth and IDC costs associated with the Company’s mobile utility applications in the overseas markets as well as lower amortization of acquired intangible assets. Non-GAAP cost of revenues decreased by 14.4% year over year to RMB391.3 million (US$62.4 million) in the first quarter of 2018.

Gross profit increased by 2.9% year over year to RMB753.9 million (US$120.2 million) in the first quarter of 2018. Non-GAAP gross profit increased by 2.7% year over year to RMB753.8 million (US$120.2 million) in the first quarter of 2018.

OPERATING INCOME AND EXPENSES

Total operating expenses decreased by 12.6% year over year to RMB617.6 million (US$98.5 million) in the first quarter of 2018. Total non-GAAP operating expenses decreased by 10.9% year over year to RMB608.5 million (US$97.0 million) in the first quarter of 2018.

Operating profit increased to RMB136.4 million (US$21.7 million) in the first quarter of 2018 from RMB26.3 million in the same period last year. Non-GAAP operating profit increased to RMB145.3 million (US$23.2 million) in the first quarter of 2018 from RMB50.7 million in the same period last year.

The Company has reported its operating profit along the following segments since the second quarter of 2017:

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Share-based compensation expenses decreased by 63.4% year over year to RMB8.9 million (US$1.4 million) in the first quarter of 2018. The decrease resulted from a combination of several factors. The Company employed an accelerated method to recognize share-based compensation expenses. In addition, a significant number of share-based awards that were granted by the Company during its IPO in 2014 approached the end of their vesting periods in 2017. Furthermore, fewer share-based awards were granted in the first quarter of 2018 than in the same period last year.

IMPAIRMENT OF INVESTMENTS

Impairment of investments were RMB58.0 million (US$9.2 million) in the first quarter of 2018 primarily due to a one-time non-cash write-down of certain convertible loans to a third-party. The loss was recorded as a non-operating item since the loans were provided for investment purposes, which is outside of the Company’s main business activity.

NET INCOME ATTRIBUTABLE TO CHEETAH MOBILE SHAREHOLDERS

Net income attributable to Cheetah Mobile shareholders was RMB70.0 million (US$11.2 million) in the first quarter of 2018. Non-GAAP net income attributable to Cheetah Mobile shareholders was RMB78.9 million (US$12.6 million) in the first quarter of 2018.

NET INCOME PER ADS

Diluted income per ADS was RMB0.42 (US$0.07) in the first quarter of 2018. Non-GAAP diluted income per ADS was RMB0.48(US$0.08) in the first quarter of 2018.

ADJUSTED EBITDA

Adjusted EBITDA (Non-GAAP) increased by 93.3% year over year to RMB168.8 million (US$26.9 million) in the first quarter of 2018.

CASH AND CASH EQUIVALENTS, RESTRICTED CASH AND SHORT-TERM INVESTMENTS BALANCE

As of March 31, 2018, the Company had cash and cash equivalents, restricted cash, and short-term investments of RMB3,355.8 million(US$535.0 million).

SHARES ISSUED AND OUTSTANDING

As of March 31, 2018, the Company had a total of 1,421,649,639 Class A and Class B ordinary shares issued and outstanding. One ADS represents 10 Class A ordinary shares.

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Business Outlook

For the second quarter of 2018, the Company expects its total revenues to be between RMB1,020 million (US$163 million) and RMB1,080 million (US$172 million). This estimate represents management’s preliminary view as of the date of this release, which is subject to change.

Conference Call Information

The Company will hold a conference call on Monday, May 21, 2018 at 8:00 a.m. Eastern Time or 8:00 p.m. Beijing Time to discuss the financial results. Listeners may access the call by dialing the following numbers:

A live and archived webcast of the conference call will also be available at the Company’s investor relations website at http://ir.cmcm.com/.

A presentation for the Company’s earnings call is available at the Company’s investor relations website.

Exchange Rate

This press release contains translations of certain Renminbi amounts into U.S. dollars at specified rates solely for the convenience of readers. Unless otherwise noted, all translations from Renminbi to U.S. dollars in this press release were made at a rate of RMB6.2726to US$1.00, the exchange rate in effect as of March 31, 2018, as set forth in the H.10 statistical release of the Federal Reserve Board. Such translations should not be construed as representations that RMB amounts could be converted into U.S. dollars at that rate or any other rate, or to be the amounts that would have been reported under accounting principles generally accepted in the United States of America (“U.S. GAAP”).

About Cheetah Mobile Inc.

Cheetah Mobile is a leading mobile Internet company with strong global vision. It has attracted hundreds of millions of monthly active users through its mobile utility products such as Clean Master and Cheetah Keyboard, casual games such as Piano Tiles 2, and live streaming product Live.me. The Company provides its advertising customers, which include direct advertisers and mobile advertising networks through which advertisers place their advertisements, with direct access to highly targeted mobile users and global promotional channels. The Company also provides value-added services to its mobile application users through the sale of in-app virtual items on selected mobile products and games. Cheetah Mobile is committed to leveraging its cutting-edge artificial intelligence technologies to power its products and make the world smarter. It has been listed on the New York Stock Exchange since May 2014.

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Safe Harbor Statement

This press release contains forward-looking statements. These statements, including management quotes and business outlook, constitute forward-looking statements under the U.S. Private Securities Litigation Reform Act of 1995. These forward-looking statements can be identified by terminology such as “will,” “expects,” “anticipates,” “future,” “intends,” “plans,” “believes,” “estimates” and similar statements. Such statements involve inherent risks and uncertainties. A number of factors could cause actual results to differ materially from those contained in the forward-looking statements, including but are not limited to the following: Cheetah Mobile’s growth strategies; Cheetah Mobile’s ability to retain and increase its user base and expand its product and service offerings; Cheetah Mobile’s ability to monetize its platform; Cheetah Mobile’s future business development, financial condition and results of operations; competition with companies in a number of industries including internet companies that provide online marketing services and internet value-added services; expected changes in Cheetah Mobile’s revenues and certain cost or expense items; and general economic and business condition globally and in China. Further information regarding these and other risks is included in Cheetah Mobile’s filings with the U.S. Securities and Exchange Commission. Cheetah Mobile does not undertake any obligation to update any forward-looking statement as a result of new information, future events or otherwise, except as required under applicable law.

Use of Non-GAAP Financial Measures

To supplement Cheetah Mobile’s consolidated financial information presented in accordance with U.S. GAAP, Cheetah Mobile uses the following non-GAAP financial measures:

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The Company believes that separate analysis and exclusion of share-based compensation expenses and the use of Adjusted EBITDA add clarity to the constituent parts of its performance from the cash perspective. The Company reviews these non-GAAP financial measures together with GAAP financial measures to obtain a better understanding of its operating performance. It uses the non-GAAP financial measures for planning, forecasting and measuring results against the forecast. The Company believes that non-GAAP financial measures are useful supplemental information for investors and analysts to assess its operating performance without the effect of share-based compensation expenses, which have been and will continue to be significant recurring expenses in its business. However, the use of non-GAAP financial measures has material limitations as an analytical tool. One of the limitations of using non-GAAP financial measures is that they do not include all items that impact the Company’s net income for the period. In addition, because non-GAAP financial measures are not measured in the same manner by all companies, they may not be comparable to other similarly titled measures used by other companies. In light of the foregoing limitations, you should not consider non-GAAP financial measure in isolation from or as an alternative to the financial measure prepared in accordance with U.S. GAAP. For more information on these non-GAAP financial measures, please see the tables captioned “Cheetah Mobile Inc. Reconciliations of GAAP and Non-GAAP Results” and “Cheetah Mobile Inc. Reconciliation of Net Income Attributable to Cheetah Mobile Shareholders to Adjusted EBITDA (Non-GAAP)” at the end of this release.

Investor Relations Contact

Cheetah Mobile Inc.

Helen Jing Zhu

Tel: +86 10 6292 7779 ext. 1600

Email: helenjingzhu@cmcm.com

ICR, Inc.

Jack Wang

Tel: +1 (646) 417-5395

Email: IR@cmcm.com

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CHEETAH MOBILE INC.

Condensed Consolidated Balance Sheets

(Unaudited, amounts in thousands of Renminbi (“RMB”) and US dollars (“US$”)

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CHEETAH MOBILE INC.

Condensed Consolidated Statements of Comprehensive Income (Loss)

(Unaudited, amounts in thousands of Renminbi (“RMB”) and US dollars (“US$”), except for number of shares and per share (or ADS) data)

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CHEETAH MOBILE INC.

Information about Segment

(Unaudited, in ’000, except for percentage)

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CHEETAH MOBILE INC.

Reconciliation of GAAP and Non-GAAP Results

(Unaudited, in ’000, except for per share data and percentage)

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CHEETAH MOBILE INC.

Reconciliation from Net Income Attributable to Cheetah Mobile Shareholders to Adjusted EBITDA (Non-GAAP)

(Unaudited, in ’000)

CHEETAH MOBILE INC.

Revenues Generated from PC-based and Mobile-based Applications and Services

(Unaudited, in ’000)

CHEETAH MOBILE INC.

Revenues Generated from Domestic and Overseas Markets

(Unaudited, in ’000)

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