Julius Fast (April 17, 1919 – December 16, 2008) was an American author of both fiction and non-fiction. In 1946 he was the first recipient of the Edgar Award given by the Mystery Writers of America for the best first novel of 1945.
Fast was born in Manhattan, the younger brother of novelist Howard Fast. Majoring in pre-med, he earned a bachelor's degree at New York University. He served in the United States Army Medical Corps for three years, serving in a blood lab in Boston. He edited Out of This World, a 1944 collection of science fiction stories while he was still in the Army.
He married author Barbara Sher in 1946. They co-wrote the 1979 book Talking Between the Lines: How We Mean More Than We Say. Their three children are: Jennie Gelfand, Dr. Melissa Morgan and Timothy Fast. In 1997, Fast and his son co-authored The Legal Atlas of the United States.
His first novel, Watchful at Night, written in 1945 while he was still serving in the Army, was given the first award presented at the inaugural Edgar Allan Poe Award in 1946 for Best First Novel by an American Author in 1945. Reviewer Isaac Anderson of The New York Times described his 1947 novel Walk in Shadow as a "profoundly moving novel of crime and punishment, telling the story of a once-honest man who becomes a murderer.