Margaret Nixon McEathron, known professionally as Marni Nixon, was an American soprano and ghost singer for featured actresses in musical films. She was the singing voice of leading actresses on the soundtracks of several musicals, including Deborah Kerr in The King and I, Natalie Wood in West Side Story, and Audrey Hepburn in My Fair Lady, although her roles were concealed from audiences when the films were released. Several of the songs she dubbed appeared on AFI's 100 Years...100 Songs list.

A playback singer or ghost singer is a singer whose performance is pre-recorded for use in films. Playback singers record songs for soundtracks, and the performers lip-sync the songs for cameras; the actual singer does not appear on the screen.