SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

Report of Foreign Private Issuer

Pursuant to Rule 13a-16 or 15d-16 of

the Securities Exchange Act of 1934

December 2019

Commission File Number: 001-37925

GDS Holdings Limited

(Registrant’s name)

2/F, Tower 2, Youyou Century Place

428 South Yanggao Road

Pudong, Shanghai 200127

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 x                      Form 40-F o

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

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

EXHIBITS

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, thereunto duly authorized.

3

Exhibit 99.1

GDS Announces Full Exercise of Underwriters’ Option to Purchase Additional ADSs

SHANGHAI, China, December 9, 2019 — GDS Holdings Limited (“GDS” or the “Company”) (Nasdaq: GDS) today announced that the underwriters of its previously announced public offering have exercised in full their option to purchase an additional 824,175 ADSs from GDS at the public offering price of US$45.50 per ADS. Each ADS represents eight Class A ordinary shares.

GDS raised a total of approximately US$276.7 million in proceeds from the public offering after the underwriters’ exercise in full of their option to purchase additional ADSs, after deducting underwriting discounts and commissions (but before expenses). GDS expects to use approximately US$190 million of the net proceeds from the offering to fund a portion of the total cash consideration and assumed liabilities in respect of its previously-announced equity purchase agreement to acquire all of the equity interests in Lanting (Beijing) Information Science and Technology Co., Ltd. and its subsidiary, Lanting Xuntong (Beijing) Science and Technology Co., Ltd., from third parties (the “Acquisition”), and use the remaining net proceeds from the offering, or all of the net proceeds from the offering if the Acquisition is not consummated, to fund other land, building and data center acquisitions, which may include the acquisitions described in the final prospectus under “Prospectus Supplement Summary—Recent Developments—Other Acquisitions,” and for general corporate purposes.

J.P. Morgan Securities LLC, RBC Capital Markets, LLC, BofA Securities, Inc. and Haitong International Securities Company Limited are acting as joint book-running managers for the proposed offering.

The securities described above are being offered by GDS pursuant to a shelf registration statement filed by GDS with the Securities and Exchange Commission (the “SEC”) that automatically became effective as of January 23, 2018. This press release shall not constitute an offer to sell or the solicitation of an offer to buy these securities, nor shall there be any offer or sale of these securities in any state or other jurisdiction in which such offer, solicitation or sale would be unlawful prior to the registration or qualification under the securities laws of any such state or other jurisdiction.

The offering is being made only by means of an effective shelf registration statement, including a preliminary prospectus supplement and final prospectus, which was filed with the SEC and is available on the SEC’s website located at http://www.sec.gov. Copies of the preliminary prospectus supplement and the final prospectus relating to this offering may be obtained from: J.P. Morgan Securities LLC, c/o Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, NY 11717, or by telephone at 866-803-9204 or by email at prospectus-eq_fi@jpmchase.com; RBC Capital Markets, LLC, Attention: Equity Syndicate, 200 Vesey Street, 8th Floor, New York, NY 10281-8098, or by telephone at (877) 822-4089 or by email at equityprospectus@rbccm.com; BofA Securities, Inc., NC1-004-03-43, 200 North College Street, 3rd floor, Charlotte, North Carolina 28255-0001, Attention: Prospectus Department, telephone: +1 (800) 294-1322, email: dg.prospectus_requests@bofa.com; or Haitong International Securities Company Limited, 22/F, Li Po Chun Chambers, 189 Des Voeux Road Central, Hong Kong, Attention: Equity Capital Markets, or by telephone at +852-2848-4333 or by email at ecm@htisec.com.

About GDS Holdings Limited

GDS Holdings Limited (Nasdaq: GDS) is a leading developer and operator of high-performance data centers in China. The Company’s facilities are strategically located in China’s primary economic hubs where demand for high-performance data center services is concentrated. The Company’s data centers have large net floor area, high power capacity, density and efficiency, and multiple redundancy across all critical systems. GDS is carrier and cloud neutral, which enables customers to connect directly to all major PRC telecommunications carriers and to the largest PRC and global cloud service providers hosted by GDS in many of its facilities. The Company has a 19-year track record of service delivery, successfully fulfilling the requirements of some of the largest and most demanding customers for outsourced data center services in China. The Company’s base of customers consists predominantly of hyper-scale cloud service providers, large internet companies, financial institutions, telecommunications and IT service providers, and large domestic private sector and multinational corporations.

Safe Harbor

This announcement contains forward-looking statements. These statements are made under the “safe harbor” provisions of the U.S. Private Securities Litigation Reform Act of 1995. These forward-looking statements can be identified by terminology such as “aim,” “anticipate,” “believe,” “continue,” “estimate,” “expect,” “future,” “guidance,” “intend,” “is/are likely to,” “may,” “ongoing,” “plan,” “potential,” “target,” “will,” and similar statements. Among other things, statements that are not historical facts, including statements about GDS Holdings’ beliefs and expectations regarding the growth of its businesses and its revenue for the full fiscal year, the business outlook and quotations from management in this announcement, as well as GDS Holdings’ strategic and operational plans, are or contain forward-looking statements. GDS Holdings may also make written or oral forward-looking statements in its periodic reports to the U.S. Securities and Exchange Commission (the “SEC”) on Forms 20-F and 6-K, in its annual report to shareholders, in press releases and other written materials and in oral statements made by its officers, directors or employees to third parties. Forward-looking statements involve inherent risks and uncertainties. A number of factors could cause GDS Holdings’ actual results or financial performance to differ materially from those contained in any forward-looking statement, including but not limited to the following: GDS Holdings’ goals and strategies; GDS Holdings’ future business development, financial condition and results of operations; the expected growth of the market for high-performance data centers, data center solutions and related services in China; GDS Holdings’ expectations regarding demand for and market acceptance of its high-performance data centers, data center solutions and related services; GDS Holdings’ expectations regarding building, strengthening and maintaining its relationships with new and existing customers; the continued adoption of cloud computing and cloud service providers in China; risks and uncertainties associated with increased investments in GDS Holdings’ business and new data center initiatives; risks and uncertainties associated with strategic acquisitions and investments; GDS Holdings’ ability to maintain or grow its revenue or business; fluctuations in GDS Holdings’ operating results; changes in laws, regulations and regulatory environment that affect GDS Holdings’ business operations; competition in GDS Holdings’ industry in China; security breaches; power outages; and fluctuations in general economic and business conditions in China and globally and assumptions underlying or related to any of the foregoing. Further information regarding these and other risks, uncertainties or factors is included in the GDS Holdings’ filings with the SEC, including its registration statement on Form F-3, as amended. All information provided in this press release is as of the date of this press release and are based on assumptions that GDS Holdings believes to be reasonable as of such date, and GDS Holdings does not undertake any obligation to update any forward-looking statement, except as required under applicable law.

For investor and media inquiries, please contact:

GDS Holdings Limited

Laura Chen

Phone: +86 (21) 2033-0295

Email: ir@gds-services.com

The Piacente Group, Inc.

Brandi Piacente

Phone: +1 (212) 481-2050

Email: GDS@tpg-ir.com

Ross Warner

Phone: +86 (10) 6508-0677

Email: GDS@tpg-ir.com