William Diehl was an American novelist and photojournalist.

Diehl was fifty years old and already a successful photographer and journalist when he decided to begin a writing career. His first novel, Sharky's Machine, which became a movie by the same name was directed by and starred Burt Reynolds. Diehl saw the movie shot on location in and around his hometown of Atlanta, Georgia.

Following the success of Sharky's Machine, Diehl relocated to St. Simons Island, GA in the early 80's where he lived for the next 15 years before going back to the Atlanta area. While living on St. Simons, he completed eight more novels, including Primal Fear, which also became a movie by the same name starring Richard Gere and Edward Norton. Diehl died at Emory University Hospital in Atlanta on November 24, 2006, of an aortic aneurism. He was a resident of Woodstock, Georgia at the time of his death and was working on his tenth novel.