The death, which occurred at a hospital where he was taken from the prison in Stockton, California, is confirmed by Durst's defense counsel.
In mid-September, a California jury announced that the American multimillionaire Robert Durst, known from HBO's "The Jinx", was guilty of the murder of his friend Susan Berman.
In October, the sentence was announced - life imprisonment without a chance of parole.
Prosecutors believed that Susan Berman knew the details of Durst's wife's disappearance and that he therefore killed Berman.
His wife Kathleen Durst disappeared in 1982 and has never been found.
Just one week after the life sentence, Durst was also charged with the murder of Kathie Durst.
At the request of the family, she was declared dead in 2017. Robert Durst divorced her in 1990.
The 78-year-old became known worldwide as the main character in HBO's acclaimed documentary series "The jinx" from 2015. He was arrested in March of the same year, the day before the last episode of the series was to be broadcast, after the documentaries with a hidden microphone had been recorded when he admits that he murdered several people.