Celsius Network LLC was a cryptocurrency company. Headquartered in Hoboken, New Jersey, Celsius maintained offices in four countries and operated globally. Users could deposit a range of cryptocurrency digital assets, including Bitcoin and Ethereum, into a Celsius wallet to earn a percentage yield, and could take out loans by pledging their cryptocurrencies as security. As of May 2022, the company had lent out $8 billion to clients and had almost $12 billion in assets under management.

In June 2022, the company gained notoriety when it indefinitely paused all transfers and withdrawals due to "extreme market conditions", resulting in steep declines in the price of bitcoin and other cryptocurrencies. On July 13, 2022, Celsius filed for Chapter 11 bankruptcy. The company announced on January 31, 2024, that it had exited bankruptcy as part of a restructuring plan that involved the distribution of assets, including a newly created bitcoin mining company, to its creditors. Celsius wound down its operations as part of its emergence from bankruptcy.

It shut down its mobile and web apps on February 29, 2024.

The company facilitated lending and borrowing for its users. Depositors earned interest by depositing qualifying cryptocurrencies, with the rate of interest dependent upon the cryptocurrency deposited (e.g., up to 6.2% interest on bitcoin). The company paid the interest in cryptocurrencies, including in its own CEL token. Borrowers paid between zero and 8.95% on bitcoin-backed loans, depending on the loan-to-value ratio. Some of the money that Celsius used to fund the loans came from hedge funds that were looking for higher yields than banks pay.

Celsius generated revenue from token sales, lending, bitcoin mining, and discretionary trading of cryptocurrencies. Celsius claimed that up to 80% of its revenue was returned to its user community through interest payments on deposits made through its platform. The company did not charge any fees to its users.

On July 7, 2022, former investment manager Jason Stone sued Celsius, alleging that the company ran a Ponzi scheme. Arkham Intelligence estimated a loss of $350 million due to improper trading protocol, which was included in Stone's lawsuit filings against Celsius. On August 23, Celsius sued Stone, alleging that he lost or stole tens of millions of US dollars' worth of cryptocurrency. The independent examiner's report filed on January 31, 2023, as part of the bankruptcy filing, said that an insider at Celsius described aspects of the business model as "very ponzi like".

In an internal memo, coin deployment specialist Dean Tappen stated "that his title at Celsius should be 'Ponzi Consultant.'"

In March 2018, Celsius raised $50 million in its initial coin offering (ICO) of the CEL digital currency. In April 2018, the CEL cryptocurrency began trading on cryptocurrency exchanges. In advance of the ICO, Celsius listed its currency as a security. In June 2018, Celsius launched its mobile app. In 2019, Celsius completed a $24 million equity round at $140 million valuation.

Celsius was a major buyer of its own token, buying CEL interest it owed to customers on the open market. Crypto analysis firm Arkham Intelligence estimated Celsius had spent $350 million on purchases since July 2019.

In August 2020, Celsius raised $20 million via an equity crowdfunding to support its operations. In the fall of 2020, the price of Celsius's currency climbed more than 230% in less than a month.

On April 16, 2021, Celsius confirmed that a security breach had occurred in its systems; a third-party server with customer data had been compromised, resulting in a portion of the company's customer list being exfiltrated and a phishing email being sent to Celsius customers.

In September 2021, authorities in a number of US states said that Celsius's interest-bearing cryptocurrency accounts constitute an unregistered securities offering. The attorney general of New Jersey ordered Celsius to stop issuing interest-bearing cryptocurrency products via a cease-and-desist order. Texas state regulators filed a notice seeking a hearing in February 2022 to determine whether to take similar action. Kentucky's securities regulator told Celsius to cease and desist from offering its interest-paying accounts in the state.

Celsius CEO Alex Mashinsky said he was "very confident" that none of Celsius's products in the United States were securities. Celsius said it was working with US states in order to provide clarity about its business operations.

On October 18, 2021, Celsius received a request for more information from New York Attorney General, Letitia James. Earlier that month, Celsius had US$400 million in new equity funding from investors.

Celsius had been using the crypto custodian Prime Trust to store some customer assets since March 2020. This relationship ended in June 2021, when Prime Trust's risk team expressed concern about Celsius's strategy of "endlessly re-hypothecating assets … lending the same assets over and over and over again to juice yields". Prime Trust founder Scott Purcell suggested that re-hypothecating "would be destined for failure as any sharp market movement in either direction would be catastrophic to such a ridiculously leveraged business model".

Celsius sued Prime Trust in August 2022, accusing the custodian of retaining $17 million worth of assets after the relationship ended.

CNBC described Celsius as "one of the largest players in the crypto lending space" in the second quarter of 2022. The company had issued loans totaling more than $8 billion, and as of May, it had almost $12 billion in assets under management. In June 2022, Celsius said it had 1.7 million customers and that it offered yields as high as 17% per year.

On June 7, in a blog post entitled "Damn the Torpedoes, Full Speed Ahead", Celsius addressed rumors that the company had lost client funds by making poor investments and that it was facing a liquidity crisis. The company dismissed these rumors as the actions of "vocal actors … spreading misinformation". The blog post denied claims that Celsius sustained significant losses as a result of the collapse of Luna in the preceding month.