Letter from an Unknown Woman is a 1948 American drama romance film released by Universal-International and directed by Max Ophüls. It was based on the 1922 novella of the same name by Stefan Zweig. The film stars Joan Fontaine, Louis Jourdan, Mady Christians, and Marcel Journet (actor).

Letter from an Unknown Woman is a novella by Austrian writer Stefan Zweig. The work first appeared in the 1 January 1922 issue of the Viennese Neuen Freien Presse, before being published in book form as part of the collection Amok: Novellen einer Leidenschaft. The novella tells the story of an author who, while reading a letter written by a woman he does not remember, gets glimpses into her life story. It is generally considered to be Zweig's most famous work of fiction.