Francesco Quinn was 48.
He reportedly collapsed in the street outside his Malibu, California home while running with his son Max. A neighbour attempted to revive him as paramedics were called, but Quinn was pronounced dead upon arrival at a nearby hospital.
Born in Rome, Quinn is the son of the late Zorba The Greek star and his second wife Iolanda.
He made his big acting break in 1986's Platoon and became a TV regular in the U.S. and U.K.
Quinn recently starred in TV dramas Justice for Natalee Holloway, Zen and Il commissario Manara. He also provided the voice for Dino in Transformers: Dark of the Moon.
His widow Valentina Castellani-Quinn tells the Malibu Patch newspaper, ""Francesco was my soulmate... I will love him forever.""