The Spiral Staircase is a 1946 American psychological horror film directed by Robert Siodmak and starring Dorothy McGuire, George Brent, and Ethel Barrymore. Set over the course of one evening, the film follows a mute young woman in an early-20th century Vermont town who is stalked and terrorized in a rural mansion by a serial killer targeting women with disabilities. Kent Smith, Rhonda Fleming, Gordon Oliver and Elsa Lanchester appear in supporting roles. It was adapted for the screen by Mel Dinelli from the novel Some Must Watch (1933) by Ethel Lina White.

The project originated with producer David O. Selznick, who purchased the rights to White's novel, intending to cast Ingrid Bergman in the lead role. Selznick subsequently sold the rights to RKO Radio Pictures, who commenced production and cast McGuire in the lead. Filming took place at the RKO Radio Pictures studio lot in Los Angeles between August and October 1945.

The Spiral Staircase premiered in New York City on February 6, 1946 and went on to become a box-office success, earning nearly $3 million. It was met by favorable critical reviews, praised for its cinematography, atmosphere, and suspense. Barrymore earned an Academy Award nomination for Best Supporting Actress for her performance in the film. In the years since its release, film scholars have noted The Spiral Staircase for its stylistic mixture of horror and film noir elements, and cited it as a progenitor of the contemporary slasher film.