The Magnificent Ambersons is a 1942 American drama film written and directed by Orson Welles. His second feature film, it is based on the 1918 novel of the same name by Booth Tarkington and stars Joseph Cotten, Dolores Costello, Anne Baxter, Tim Holt, Agnes Moorehead and Ray Collins. Welles provides the voiceover narration.

Tarkington's novel had originally been filmed in 1925 by Vitagraph Pictures, starring Cullen Landis, Alice Calhoun and Allan Forrest, and directed by David Smith. Welles adapted it for radio in 1939 for the Mercury Theatre of the Air. The only actor from that production who also appeared in the film was Ray Collins.

Welles lost control of the editing of The Magnificent Ambersons to RKO, and the final version released to audiences differed significantly from his vision for the film. More than an hour of footage was cut by the studio, and a new, happier ending was shot and tacked on. Although Welles's extensive notes for how he wished the film to be cut survived, the excised scenes did not.

A TV movie was made in 2002 using the Welles screenplay and his editing notes. It was directed by Alfonso Arau and starred Madeleine Stowe, Bruce Greenwood, Jonathan Rhys Meyers, Gretchen Mol and Jennifer Tilly. This film does not, however, strictly follow Welles's screenplay. It lacks several scenes that are in the 1942 version, and also has essentially the same happy ending.

Even in its radically altered form, the 1942 film is often regarded as among the best American films ever made, a distinction it shares with Welles' first film, Citizen Kane.

In 1991, The Magnificent Ambersons was selected for preservation in the United States National Film Registry by the Library of Congress as being "culturally, historically, or aesthetically significant". The film was included in Sight and Sound's 1972 list of the top ten greatest films ever made, and again in 1982's list.