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.

In 1912, Lettinger played his first film role in Das Geheimnis von Monte Carlo.

His best-known film is perhaps The Cabinet of Dr. Caligari (1920), where Lettinger portrayed Dr. Olsen.