William Devane (born September 5, 1937) is an American film and television actor.

Devane was born in Albany, New York, the son of Joseph (Joe) Devane, who was President Franklin D. Roosevelt's chauffeur when he was Governor of New York. Devane graduated from the American Academy of Dramatic Arts in New York.

Devane is perhaps most widely recognized for his ten years as the villainous Greg Sumner on the drama series Knots Landing, and his role as President Kennedy in the TV film The Missiles of October, about the Cuban Missile Crisis. Devane has also appeared in such films as McCabe & Mrs. Miller (1971), Family Plot (1976), Marathon Man (1976), Rolling Thunder (1977), The Bad News Bears in Breaking Training (1977), Testament (1983), Forgotten Sins (1996), Payback (1999), and Space Cowboys (2000).

Devane has played members of the United States Cabinet on two different evening dramas. In 2004, he guest-starred as United States Secretary of State and potential vice-presidential nominee Lewis Berryhill on The West Wing. In 2005, he joined the cast of 24 as United States Secretary of Defense James Heller in the show's fourth season. During the middle of the season, however, Devane was one of several cast members to be written out of the series. He returned for one more episode later that season, and again in the show's fifth and sixth seasons (2006). In his role on The West Wing, Devane appeared in several scenes with the show's fictional President Josiah Bartlet, played by Martin Sheen. Devane and Sheen also appeared together as President Kennedy and his brother Robert F. Kennedy, respectively, 30 years earlier in The Missiles of October.

In 2004, Devane also starred in three episodes of Stargate SG-1, as President Henry Hayes. Most recently, he starred in the short-lived ABC sitcom, Crumbs and also plays Brian Davis' father, a real estate broker, in the ABC series What About Brian. And more recently in 2008, he starred in Russ Emanuel's "Chasing the Green" alongside Jeremy London, Ryan Hurst, and Robert Picardo.

William Devane, the movie and television actor, was born in Albany, New York, the son of Joseph Devane, who served as Franklin Delano Roosevelt's chauffeur when he was Governor of New York. After graduating from New York City's American Academy of Dramatic Arts, he appeared on-stage. He finally made his Broadway debut in "The Watering Place" with Shirley Knight (I), a flop that lasted but one performance. (He was more successful with "The Chinese and Dr. Fish" during the 1970 season, which lasted three weeks. His sole Broadway directorial effort, the Vietnam War drama "G. R. Point," lasted for 32 performances in 1979 and brought Michael Jeter a 1979 Theatre World Award.) He made his movie debut as a revolutionary in the independently produced In the Country (1967) and began appearing on series TV. He had a small but memorable part as the lawyer committed to free-enterprise in Robert Altman (I)'s masterpiece McCabe & Mrs. Miller (1971) in 1971, but what made his reputation was his turn as President John F. Kennedy in the Missiles of October, The (1974) (TV), a 1973 telefilm about the Cuban Missile Crisis. He made a bid for stardom with major roles in Alfred Hitchcock (I)'s Family Plot (1976) and John Schlesinger (I)'s Marathon Man (1976) (both 1976) and Bad News Bears in Breaking Training, The (1977) (1977), as well as roles in Schlesinger's Yanks (1979) and the TV adaptation of James Jones (I)' classic barracks drama "From Here to Eternity" (1979) (mini). However, any chances for a successful movie career essentially were doomed by the monumental failure of Schlesinger's comedy Honky Tonk Freeway (1981), one of the great flops its time, bringing in only $2 million at the box office against a $24 million budget. Devane moved over to nighttime series TV, playing the cad Greg Sumner on the night-time soap opera "Knots Landing" (1979) for 10 years. Because of his resemblance to President Kennedy and his ability to master a Kennedyesque Boston accent, Devane continues to be in demand as politicians, including presidents, in such shows as "West Wing, The" (1999), "24" (2001), and "Stargate SG-1" (1997).