Who wrote An American in Paris?

Depends on whether you mean the originating musical composition... An American in Paris is a symphonic composition by American composer George Gershwin, composed in 1928. Inspired by time Gershwin had spent in Paris, it is in the form of an extended tone poem evoking the sights and energy of the French capital in the 1920s. It is one of Gershwin's best-known compositions. Or if you mean the screenplay for the movie...An American in Paris is a 1951 MGM musical film inspired by the 1928 orchestral composition by George Gershwin. Starring Gene Kelly, Leslie Caron, and Oscar Levant, the film is set in Paris, and was directed by Vincente Minnelli from a script by Alan Jay Lerner. The music is by George Gershwin, with lyrics by his brother Ira, with additional music by Saul Chaplin, the music director.