Rudolf Lettinger (26 October 1865 in Hamburg – 21 March 1937 in Berlin-Schöneberg) was a German stage and film actor. He made his stage debut in 1883 when he played the role of Kosinsky in Friedrich Schiller's drama The Robbers. Some of his more prominent roles in his prestigious stage career were Cyrano de Bergerac and Gessler in William Tell. He also worked with acclaimed stage director Max Reinhardt. In 1912, Lettinger played his first film role in Das Geheimnis von Monte Carlo. Lettinger appeared in over 90 films until 1931, mostly as a supporting actor. His best-known film is perhaps The Cabinet of Dr. Caligari (1920), where Lettinger portrayed Dr. Olsen.