Doctor X is a 1932 American pre-Code mystery horror film produced jointly by First National and Warner Bros. Based on the 1931 play originally titled The Terror by Howard W. Comstock and Allen C. Miller, it was directed by Michael Curtiz and stars Lionel Atwill, Fay Wray and Lee Tracy.

Doctor X was produced before the Motion Picture Production Code was enforced. Themes such as murder, rape, cannibalism and prostitution are interwoven into the story. The film was one of the last produced, along with Warner Bros.' subsequent Mystery of the Wax Museum (1933), in the early two-color Technicolor process. Separate black-and-white prints were shipped to small towns and foreign markets, while color prints were reserved for major cities.

In the film, there are a series of murders in New York City. Each murder takes place under the full moon, and each body has been cannibalized post-mortem. Dr. Xavier is asked to provide his medical insight into the crimes, though the police actually suspect him and other people in Xavier's medical academy. The Moon Killer is conducting his own experiments, in an attempt to collect samples from his victims.