Forsythe made his name as oil baron Blake Carrington in US drama Dynasty for which he won two Golden Globe awards.
He was also the voice of Charlie in 1970s detective show Charlie’s Angels.
Forsythe died at home near Los Angeles after contracting pneumonia, his family said.
Fans in Hollywood paid tribute to the star, whose career spanned seven decades.
Dynasty was cancelled in 1989 but Forsythe was back on the big screen over a decade later when he reprised his role in the Charlie’s Angels movies alongside Cameron Diaz, Bill Murray and Drew Barraymore.