Marathon Man is a 1974 conspiracy thriller novel by William Goldman. It was Goldman's most successful thriller novel, and his second suspense novel.

William Goldman was an American novelist, playwright, and screenwriter. He first came to prominence in the 1950s as a novelist before turning to screenwriting. Among other accolades, Goldman won two Academy Awards in both writing categories—once for Best Original Screenplay for Butch Cassidy and the Sundance Kid (1969) and once for Best Adapted Screenplay for All the President's Men (1976).