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 Head of Janus (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. Mayer was a fundamental figure in the dramatic and narrative establishment of both German Expressionist cinema and Kammerspielfilm.