The Czech news agency CTK quoted Martina Forman as saying her husband died suddenly on Friday after a short illness.
Forman died about 2 a.m. Saturday at Danbury Hospital, near his home in Warren, Connecticut, according to a statement released by the former director's agent, Dennis Aspland. Later in his career he was also known for The People vs. Larry Flynt (1996) and Man on the Moon (1999), both of which centered on American subjects.
Forman first stormed onto the worldwide scene in 1964 with his film Black Peter, followed by The Loves of a Blonde in 1965 (which was nominated for an Oscar for best foreign-language film) and The Firemen's Ball in 1967.
The 1975 film, which starred Jack Nicholson as a rebellious ringleader inside the institution, was a commercial and artistic breakthrough for Forman and swept the top honors at the Academy Awards, winning for best picture, best director, best actor and best actress (Louise Fletcher as the stone-hearted Nurse Ratched).
However, that wasn't the end of it as Forman went on to win his second Oscar for the 1984 Hollywood film "Amadeus", a biopic of Wolfgang Amadeus Mozart.
"In his films you can see the author", he said.
American writer-producer Larry Karaszewski, who made two films (including "Larry Flynt") with Forman, said the filmmaker was "our friend and our teacher".
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His debut as director, Black Peter, about a teenager in his first job, incurred the dislike of the Communist authorities for its irreverent attitude, but after its prizewinning appearance at the Locarno film festival enabled Forman to continue directing.
He was born Jan Tomas Forman on February 18, 1932, the youngest of three brothers, in Caslav, a town outside of Prague.
- 1940: His parents, members of the resistance against the Nazis, are deported to the Buchenwald and Auschwitz concentration camps where they die.
"When we started to make our films, they were really Czech films about Czech society and Czech little people - and who cares about Czech little people?"
In August 1968 Czechslovakia was invaded by Warsaw Pact forces aiming to suppress Alexander Dubcek's liberalising reforms; Forman opted to stay in the USA, were he was joined by fellow director Ivan Passer. After attempting to get the rights to the musical Hair, Forman began work on an original screenplay, for the film Taking Off.
Forman directed almost two dozen films in his career, but he enjoyed his greatest critical and commercial success during the '70s and '80s.
Forman rebounded four years later with the iconic "One Flew Over the Cuckoo's Nest", which won five Academy Awards, including one for himself as director. With lavish costumes, Mozart's ravishing music and exceptional performances from actors Tom Hulce as Mozart and F. Murray Abraham as Salieri, Forman scored another artistic triumph. Their twin sons Andrew and James were named after Kaufman and Jim Carrey, who portrayed the madcap comic in Man on the Moon.