Forsythe was born on September 11, 1917, in Macon, Missouri. He earned great acclaim and a 1979 Tony Award for Best Featured Actor in a Musical for his performance as Sheriff Ed Earl Dodd in The Best Little Whorehouse in Texas. His other Broadway credits include The Cellar and the Well, Miss Lonelyhearts, Who's Afraid of Virginia Woolf?, The Right Honourable Gentleman, Malcolm, A Delicate Balance, The Birthday Party, Harvey, The Engagement Baby, The Freedom of the City, A Texas Trilogy: The Last Meeting of the Knights of the White Magnolia, A Texas Trilogy: The Oldest Living Graduate and Some Americans Abroad.
Forsythe spent more than three decades playing David Stewart on the CBS soap opera As the World Turns, which he departed in 1990. His film credits include Dead of Night, Silkwood, End of the Line, Chances Are and Species II.
Forsythe is survived by his wife, two sons and four grandchildren.