Zelig is a 1983 American satirical mockumentary comedy film written, directed by and starring Woody Allen as Leonard Zelig, a nondescript enigma, who, apparently out of his desire to fit in and be liked, unwittingly takes on the characteristics of strong personalities around him. The film, presented as a documentary, recounts his period of intense celebrity during the 1920s, including analyses by contemporary intellectuals.

The film received critical acclaim and was nominated for numerous awards, including the Academy Awards for Best Cinematography and Costume Design.

Zelig was photographed and narrated in the style of 1920s black-and-white newsreels, which are interwoven with archival footage from the era and re-enactments of real historical events. Color segments from the present day include interviews of real cultural figures, such as Saul Bellow and Susan Sontag, and fictional ones.

Set in the 1920s and 1930s, the film concerns Leonard Zelig (Woody Allen), a nondescript man who has the ability to transform his behavior and demeanor to that of the people who surround him. He is first observed at a party by F. Scott Fitzgerald, who notes that Zelig related to the affluent guests in a refined Boston accent and shared their Republican sympathies, but while in the kitchen with the servants, he adopted a coarser tone and seemed to be more of a Democrat. He soon gains international fame as a "human chameleon".

Interviewed in one of the witness shots, psychologist Bruno Bettelheim makes the following comment:

The question of whether Zelig was a psychotic or merely extremely neurotic was a question that was endlessly discussed among his doctors. Now I myself felt his feelings were really not all that different from the normal, what one would call the well-adjusted, normal person, only carried to an extreme degree, to an extreme extent. I myself felt that one could really think of him as the ultimate conformist.

Dr. Eudora Fletcher (Mia Farrow) is a psychiatrist who wants to help Zelig with this strange disorder when he is admitted to her hospital. Through the use of hypnotism, she discovers Zelig yearns for approval so strongly that he physically changes to fit in with those around him. Dr. Fletcher eventually cures Zelig of his compulsion to assimilate, but goes too far in the other direction; for a brief period he is so intolerant of others' opinions that he gets into a brawl over whether or not it is a nice day.

Dr. Fletcher realizes that she is falling in love with Zelig. Because of the media coverage of the case, both patient and doctor become part of the popular culture of their time. However, fame is the main cause of their division. Numerous women claim that he married and impregnated them, causing a public scandal. The same society that made Zelig a hero destroys him.