Nathaniel D. Mann (1866–1915) was an American composer best known for his work with L. Frank Baum. He composed at least two songs with Baum, "Different Ways of Making Love" and "It Happens Ev'ry Day," and another with John Slavin, "She Didn't Really Mind the Thing at All," for The Wizard of Oz stage musical in 1902, and in 1908, composed the first original film score (27 cues) for The Fairylogue and Radio-Plays, one of the earliest feature-length fiction films (and the earliest film adaptations of the novels The Wonderful Wizard of Oz, The Marvelous Land of Oz, Ozma of Oz, John Dough and the Cherub, and Dorothy and the Wizard in Oz, presented by Baum himself), which debuted September 24, 1908. With Baum, he also composed the musical The King of Gee-Whiz (dated February 23, 1905), which went through various titles such as Montezuma (November 1902), King Jonah XIII (September 1903), and The Son of the Sun (1905). This was collaboration with and based on a novel by Emerson Hough, which was never completed and the extant scenario published in 1969.

His other works include The Sultan of Sulu with George Ade and Alfred George Whathall (1902), "Moon, Moon," sung by Christie MacDonald in The Toreador (1902), The Mayor of Tokio with William Frederick Peters (1905), The Alaskan with R. F. Carroll (1909), Imam : A Mohammedan Serenade (1912), and the one-act ballet, La Naissance de la Rose (Opus 52) (1914). Much of his work consisted of coon songs.

He was a brother of actors Louis Mann and Sam Mann. He died in San Francisco on April 12, 1915.