King of the Underworld is a 1939 American crime drama film starring Humphrey Bogart as a gangster and Kay Francis as a doctor forced to treat him. It was directed by Lewis Seiler. It is a remake of the 1935 film Dr. Socrates, which was based on a short story by W. R. Burnett.

Christopher Joseph Devlin, better known as Joe Devlin, was a vaudeville and burlesque performer, and American actor with over 170 film and television credits.