Nathaniel Davis Ayer (August 5, 1887 – September 19, 1952), usually billed as Nat D. Ayer, 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.
Ayer was born Nathaniel Davis in Boston, Massachusetts. His first big hit was the song "Oh, You Beautiful Doll" (1911), with words by A. Seymour Brown (1885–1952). He wrote songs for Broadway revues and musical comedies including Miss Innocence (1908), The Newlyweds and their Baby (1909), Ziegfeld Follies of 1909, The Echo (1910), A Winsome Widow, The Wall Street Girl, Let George Do It (all 1912) and Ziegfeld Follies of 1916.
Ayer first visited London as a member of the Ragtime Octet in the years before the First World War. In 1912 he contributed to the West End revue Hullo, Ragtime the song "You’re My Baby" with words by Brown. In 1913 he appeared at the Tivoli music hall in the Strand, with Harry Williams, performing songs of their own composition, with Ayer at the piano. Later in the same year, the two appeared in The Hippodrome Revue, when The Times described them thus: