The Magnificent Ambersons is a 1942 American period drama written, produced, and directed by Orson Welles. Welles adapted Booth Tarkington's Pulitzer Prize–winning 1918 novel about the declining fortunes of a wealthy Midwestern family and the social changes brought by the automobile age. The film stars Joseph Cotten, Dolores Costello, Anne Baxter, Tim Holt, Agnes Moorehead and Ray Collins, with Welles providing the narration.

Welles lost control of the editing of The Magnificent Ambersons to RKO, and the final version released to audiences differed significantly from his rough cut of the film. More than an hour of footage was cut by the studio, which also shot and substituted a happier ending. Although Welles's extensive notes for how he wished the film to be cut have survived, the excised footage was destroyed. Composer Bernard Herrmann insisted his credit be removed when, like the film itself, his score was heavily edited by the studio.

Even in the released version, The Magnificent Ambersons is often regarded as among the greatest films of all time, a distinction it shares with Welles's first film, Citizen Kane. The film was nominated for four Academy Awards, including Best Picture, and it was added to the National Film Registry of the Library of Congress in 1991.