Goldman grew up in a Jewish family in the Chicago suburb of Highland Park, Illinois. He obtained a BA degree at Oberlin College in 1952 and a MA degree at Columbia University in 1956.
According to Goldman's memoir, Adventures in the Screen Trade, Goldman began writing when he took a creative writing course in college. He did not originally intend to become a screenwriter. His main interests were poetry, short stories, and novels. William Goldman published five novels and had three plays produced on Broadway before he began to write screenplays. He wrote mostly serious literary works until the death of his first agent when he then began writing thrillers starting with Marathon Man.
Goldman researched Butch Cassidy and the Sundance Kid for eight years and used Harry Longbaugh (a variant spelling of the Sundance Kid's real name) as his pseudonym for No Way to Treat a Lady. After deciding he did not want to write a cowboy novel, he turned the story into his first original screenplay and sold it for a record $400,000. He went on to use several of his novels as the foundation for his screenplays, such as the The Princess Bride. Among the many other popular scripts written by Goldman are The Stepford Wives (1975), Marathon Man (based on his novel) (1976); A Bridge Too Far (1977); Misery (1990); Chaplin (1992); Maverick (1994) and Absolute Power (1997).
In the 1980s he wrote a series of memoirs looking at his professional life on Broadway and in Hollywood. (In one of these he famously sized up the entertainment industry by concluding: "Nobody knows anything.") For many years he often has been called in as an unaccredited script doctor on troubled Hollywood projects, such as Twins, A Fish Called Wanda, Chaplin, Malice, Last Action Hero and Fierce Creatures.
Goldman has won two Academy Awards: an Academy Award for Writing Original Screenplay for Butch Cassidy and the Sundance Kid, and an Academy Award for Writing Adapted Screenplay for All the President's Men. He has also won two Edgar Awards, from the Mystery Writers of America, for Best Motion Picture Screenplay: for Harper in 1967, and for Magic (adapted from his own 1976 novel) in 1979.
He had been estranged for many years from his brother, playwright James Goldman, before James's death in 1998. He was married to Ilene Jones until their divorce in 1991. The couple had two daughters.