Shadow of a Doubt is a 1943 film noir film which tells the story of a young woman who thinks that her uncle might be a serial killer. It stars Teresa Wright, Joseph Cotten, Macdonald Carey, Henry Travers and Hume Cronyn.

The movie was written by Gordon McDonell, Thornton Wilder, Sally Benson and Alma Reville. It was directed by Alfred Hitchcock.

It was nominated for an Academy Award for Best Writing, Original Story (Gordon McDonell),

Alfred Hitchcock often said that this was his favorite film. It was remade as Step Down to Terror in 1958. The original film has been deemed "culturally significant" by the United States Library of Congress and selected for preservation in the National Film Registry.