The actor, who was also the voice of Charlie in the Charlie's Angels TV series and films, played Blake Carrington in the 1980s soap.
Forsythe died on Thursday in Santa Ynes, California, from complications of pneumonia after a year-long battle with cancer, his publicist said yesterday.
His acting career began in the 1940s and he appeared in the Alfred Hitchcock films The Trouble With Harry and Topaz, but was best known for his depiction of the oil tycoon Carrington in Dynasty. He played the character from 1981 to 1989 and earned three Emmy nominations, but never won.
With his full head of silver hair, tanned face and smooth voice, Forsythe, as Blake Carrington, attracted the ardour of millions of female television viewers.
Forsythe was also well known for playing the role of Charlie in Charlie's Angels from 1976 to 1981, even though he never showed his face.
His voice was usually heard over the phone as he gave the "Angels" their next mission. Forsythe reprised the role for two feature film follow-ups.
He said in an interview in 1981: "I figure there are a few actors, like Marlon Brando, George C Scott and Laurence Olivier, who have been touched by the hand of God. I'm in the next bunch."
In a statement, his family said: "Thankfully, he died as he lived his life… with dignity and grace, after a year-long struggle with cancer."