His son, John Christopher, said the actor died from non-lung small cell carcinoma at his home in Pasadena.
He was 84.
The actor played the role of Father John Mulcahy on "M*A*S*H" from 1972 to 1983 and in the follow-up series "After M*A*S*H*" from 1983 to 1985.
He also had parts in the movies "The Fortune Cookie," "With Six You Get Eggroll," and the TV show "Gomer Pyle, U.S.M.C."
William Christopher leaves behind his wife Barbara and his sons John and Ned.
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