"If You Were the Only Girl (In the World)" is a popular song, written by Nat D. Ayer with lyrics by Clifford Grey. It was written for the musical revue The Bing Boys Are Here, which premièred on 19 April 1916 at the Alhambra Theatre in Leicester Square, London. The song was originally performed as a duet between Lucius Bing, played by George Robey, and his love interest Emma, originated by Violet Loraine.

Clifford Grey was an English songwriter, librettist, actor and screenwriter. His birth name was Percival Davis, and he was also known as Clifford Gray.