Shadow of a Doubt is a 1943 American psychological thriller film noir directed by Alfred Hitchcock, and starring Teresa Wright and Joseph Cotten. Written by Thornton Wilder, Sally Benson, and Alma Reville, the film was nominated for an Academy Award for Best Story for Gordon McDonell.

The story follows Charlotte "Charlie" Newton and her family who live in very quiet Santa Rosa, California. An unexpected visit by Charles Oakley, her charming and sophisticated Uncle Charlie, brings much excitement to the family and the small town. That excitement turns to fear as young Charlie slowly realizes her uncle is in fact a wanted serial murderer known as the "Merry Widow" killer. The fear escalates when Oakley realizes she knows his secret.

In 1991, the film was selected for preservation in the United States National Film Registry by the Library of Congress, being deemed "culturally, historically, or aesthetically significant". Hitchcock's favorite of all his films, Shadow of a Doubt was also the one he enjoyed making the most.