Nathaniel Davis Ayer (August 5, 1887 in Boston, Massachusetts - September 19, 1952 in London, England) was a British-U.S. composer of popular music, including the hits Oh, You Beautiful Doll (1911) and If You Were the Only Girl (In the World) (1916). He was the father of actor Harold Ayer (1916–2003), who lived in California, and Nat Ayer Jr. (d. 2004), who lived in Pimlico, London, having sailed to the UK with his father in 1914.
Ayer composed several hit musical comedies and revues, including Yes, Uncle!, The Bing Boys are Here, The Bing Boys on Broadway, and Baby Bunting. He contributed songs to others, like Phi-Phi (1922).