Sam Bankman-Fried has lost his bid to overturn his fraud conviction and 25-year prison sentence over the collapse of the FTX cryptocurrency exchange he founded.
The decision was handed down by a three-judge panel of the Manhattan-based 2nd US Circuit Court of Appeals.
"The government's evidence against him was, conservatively stated, robust," the judges wrote in a 42-page opinion.
Bankman-Fried's lawyers did not immediately respond to a request for comment.
Bankman-Fried, who had been one of the cryptocurrency sector's most influential figures and a multi-billionaire before FTX's spectacular collapse in 2022, was found guilty on seven felony charges by a federal jury in Manhattan in 2023.
Prosecutors with the Manhattan US Attorney's office said he stole $US8 billion ($A11 billion) from FTX customers in what they termed a "fraud of epic proportions".
Bankman-Fried had pleaded not guilty to the two counts of fraud and five counts of conspiracy that he faced.
At his trial, he admitted to making mistakes running FTX but testified that he never stole funds.
In appealing the conviction, Bankman-Fried's defence lawyers argued that US District Judge Lewis Kaplan, who oversaw the trial, improperly prevented Bankman-Fried from introducing evidence to back up his belief that FTX had enough funds to cover customer withdrawals.
Prosecutors countered that evidence at trial, including testimony from three of Bankman-Fried's former deputies, overwhelmingly proved his guilt.
Those former employees, who pleaded guilty and agreed to co-operate with prosecutors, testified that he directed them to raid FTX customer funds to plug losses at Alameda Research, Bankman-Fried's crypto-focused hedge fund.
At his March 2024 sentencing hearing, Kaplan said Bankman-Fried knew his actions were wrong but "made a very bad bet about the likelihood of getting caught".
Bankman-Fried is being held at a low-security federal prison near Santa Barbara, California.
He is eligible for release in 2044.
Bankman-Fried was a rising star in the rough-and-tumble crypto industry who burnished his reputation with lavish philanthropic and political donations.