"Mostly Martha" is a popular song written by Ralph Sterling (music) and Dorcas Cochran (lyrics).
It first reached the Billboard magazine charts on January 7, 1956.
The melody of the song is borrowed from the tenor aria usually known by its Italian title, "M'appari", composed in 1847 by the German Friedrich von Flotow.
It was written for his opera L'Ame en Peine, but famous for its inclusion in his best-known work, Martha.
The melody appears as part of the background music in Alfred Hitchcock's 1954 film Rear Window.