The 66-year-old hedge fund manager, known for friendships with high-profile figures such as current US President Donald Trump, former President Bill Clinton and Britain's Prince Andrew, had pleaded not guilty to sex trafficking and conspiracy charges. He was being held without bail since his arrest on July 6.
Some US media reports said that Epstein hanged himself in his cell and his body was discovered at 7.30 a.m. (local time) at the facility in New York, while others said that he was found in cardiac arrest early Saturday and taken to a hospital where he died.
His death comes a day after unsealed documents in New York revealed the extent of his abuse of young women at his home in Palm Beach, New York and the Virgin Islands.
Epstein was accused of paying girls under the age of 18 to perform sex acts at his Manhattan and Florida mansions between 2002 and 2005.
He was under suicide watch after being found unconscious three weeks ago in his cell at New York's Metropolitan Correctional Centre. He had suffered injuries to his neck in what appeared to be a suicide attempt or jailhouse assault.
Epstein was convicted in 2008 on Florida charges of soliciting and procuring a person under 18 for prostitution.
He avoided what could have been a lengthy prison sentence under a plea deal with then-US Attorney Alex Acosta. The deal drew intense scrutiny and led Acosta to resign as Trump's Labor Secretary.
Hundreds of pages of court documents unsealed on Friday in New York federal court alleged new details of sexual abuse claims against Epstein and several associates.
At the heart of the documents connected to a 2015 defamation case are allegations by a woman, Virginia Roberts Giuffre, who claimed that Epstein kept her as a teenage "sex slave" and that he was assisted in his efforts by a British woman, Ghislaine Maxwell.
( With inputs from IANS )