Nathaniel Davis Ayer (August 5, 1887 – September 19, 1952) was an American composer, pianist, singer and actor. He made most of his career composing and performing in England in Edwardian musical comedy and revue. He also contributed songs to Broadway shows, including some of the Ziegfeld Follies.
Ayer's most successful shows were the World War I hits The Bing Boys Are Here (1916) and Yes, Uncle (1917). His best-known Broadway song was "Oh, You Beautiful Doll" (1911). Of his many songs composed for London shows, his most famous is probably "If You Were the Only Girl In the World" (1916). After the war, he had less success and was declared bankrupt in 1938.