GSUM Gridsum Holdings Inc

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 March 2019

Commission File Number: 001-37871

Gridsum Holding Inc.

South Wing, High Technology Building

No. 229 North 4th Ring Road

Haidian District, Beijing 100083

People’s Republic of China

(86-10) 8261-9988

(Address, including zip code, and telephone number, including area code, of Registrant’s 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):  ☐

On March 4, 2018, Gridsum Holding Inc. (the “Company”) completed the transactions contemplated by the share subscription agreement (the “Subscription Agreement”) dated February 28, 2019 between the Company and certain equity investment firms (the “Investors”). In accordance with the Subscription Agreement, the Investors made an aggregate investment of approximately US$11.1 million by subscribing for 3,461,902 newly issued Class B ordinary shares of the Company, par value US$0.001 per share, at a subscription price of US$3.20 per share. In connection with this investment, the Company entered into a registration rights agreement with the Investors, which is included as an exhibit to this Form 6-K.

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