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 July 2025

Commission File Number: 001-39258

BTC Digital Ltd.

61 Robinson Road Level 6 & 7

#738, Singapore 068893

(Address of principal executive office)

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

Form 20-F ☒ Form40-F ☐

On July 21, 2025, BTC Digital Ltd. issued a pressrelease announcing the expansion of its Ethereum strategic reserve. A copy of the press release is filed as Exhibit 99.1 to this reportand is incorporated herein by reference. The press release is qualified in its entirety by reference to the full text of such exhibit.

SIGNATURES

Pursuant to the requirements of the Securities ExchangeAct of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

	BTC Digital Ltd.

Date: July 21, 2025	By:	/s/ Siguang Peng
	Name:	Siguang Peng
	Title:	Chief Executive Officer

EXHIBIT INDEX

Exhibit No.		Description
99.1		Press Release

Exhibit 99.1

BTC Digital Expands Ethereum Strategic Reserve with $5 MillionETH Acquisition; Holdings Reach 2,135 ETH

SINGAPORE, July 21,2025 /PR Newswire/ – BTC Digital Ltd. (“BTCT” or the “Company”) (NASDAQ: BTCT),a leading blockchain technology company, today announced it has further advanced its Ethereum(ETH) strategic reserve with a new $5 millionpurchase of ETH. As of the date of this release, BTCT’s cumulative holdings amount to 2,135 ETH,marking another decisive step in building a long-term strategic asset pool.

Key Highlights

New Acquisition: $5 million in ETH

Total Reserve: 2,135 ETH

This latest investment is a critical component of BTCT’s ongoingEthereum strategy, following last week’s successful $6 millionfinancing round. By continuously increasing its ETH holdings, the Company underscores its confidence in Ethereum’s long-term valueand solidifies its role as a committed participant in the Ethereum ecosystem.

Looking ahead, BTCT plans to maintain its disciplined acquisition cadence,leveraging market conditions and corporate strategy to rapidly expand its ETH reserve.

“Ethereum is more than just a digital asset—it represents thefoundational infrastructure of the global digital economy,” said Mr. Siguang Peng, CEO of BTCT. “Our 2,000+ ETHreserve is only the beginning. We remain unwavering in our commitment to this strategic direction.”

About BTC Digital Ltd.

BTC Digital Ltd. is a blockchain technologycompany, with a long-term strategy to create value across the metaverse, blockchain and cryptocurrency mining industry. The Company iscommitted to developing blockchain related businesses in North America, including cryptocurrency mining, mining farm construction, miningpool and data center operation, and miner accessories business.

For more information, please visit: https://btct.investorroom.com/

Safe Harbor Statement

This news release contains forward-looking statementswithin the meaning of Section 21E of the Securities Exchange Act of 1934, as amended, and as defined in the U.S. Private Securities LitigationReform Act of 1995. These forward-looking statements can be identified by terminology such as "will", "expects", "anticipates","future", "intends", "plans", "believes", "estimates", "target", "goingforward", "outlook" and similar statements. Such statements are based upon management's current expectations and currentmarket and operating conditions and relate to events that involve known or unknown risks, uncertainties and other factors, all of whichare difficult to predict and many of which are beyond the Company's control, which may cause the Company's actual results, performanceor achievements to differ materially from those in the forward-looking statements. Further information regarding these and other risks,uncertainties or factors is included in the Company's filings with the U.S. Securities and Exchange Commission. The Company does not undertakeany obligation to update any forward-looking statement as a result of new information, future events or otherwise, except as requiredunder law.

For investor and media inquiries, please contact:

ir@btct.us