Ruja Ignatova is accused of defrauding investors out of $4bn (£3.3bn) by selling a fake cryptocurrency called OneCoin.
A Bulgarian woman, also known as “Cryptoqueen”, has been added to the FBI’s list of its 10 most-wanted fugitives.
Ignatova, a German citizen, disappeared in late 2017 after bugging a flat belonging to her American boyfriend and learning he was cooperating with an FBI probe into OneCoin, prosecutors said.
She boarded a flight from Bulgaria to Greece and has not been seen since.
The FBI is offering a $100,000 (£82,463) reward for information leading to her capture.
Ignatova is believed to travel with armed guards and/or associates, the bureau said, adding she may have had plastic surgery or otherwise altered her appearance.
The 42-year-old was charged in 2019 with eight counts including wire fraud and securities fraud for running the Bulgaria-based OneCoin Ltd as a pyramid scheme.
Prosecutors say the company offered commissions for members to entice others to buy a worthless cryptocurrency.
“She timed her scheme perfectly, capitalising on the frenzied speculation of the early days of cryptocurrency,” said Damian Williams, the top federal prosecutor in Manhattan.
He described OneCoin as “one of the largest Ponzi schemes in history”.
The FBI adds fugitives to its “Most Wanted” list when it believes the public may be able to help with tracking down suspects.
Michael Driscoll, the FBI’s assistant director-in-charge in New York, said Ignatova “left with a tremendous amount of cash”.
“Money can buy a lot of friends, and I would imagine she’s taking advantage of that.”