Carl Mayer (20 November 1894 – 1 July 1944) was an Austrian screenwriter who wrote or co-wrote the screenplays to The Cabinet of Dr. Caligari (1920), The Haunted Castle (1921), Der Letzte Mann (1924), Tartuffe (1926), Sunrise: A Song of Two Humans (1927), and 4 Devils (1928), most of them being films directed by F. W. Murnau.

Born into a Jewish family, Mayer was the son of a stock speculator who committed suicide, forcing the young Carl to leave school at 15, and go to work as a secretary.

In 1933, shortly after working with Béla Balázs on the script for Das Blaue Licht (1932), directed by Leni Riefenstahl, he moved to London to escape the Nazi regime.

Near the end of his life, he wanted to make a documentary film on London, but due to anti-German sentiment and difficult economic conditions, he was unable to find a producer.

He was buried in the eastern section of Highgate Cemetery, south of the entrance, facing the grave of William Friese-Greene, in London.