Gustaf Gründgens (22 December 1899 – 7 October 1963), born Gustav Heinrich Arnold Gründgens, was one of Germany's most famous and influential actors of the 20th century, and artistic director of theatres in Berlin, Düsseldorf, and Hamburg. His career continued unimpeded through the years of the Nazi regime; the extent to which this can be considered as deliberate collaboration with the Nazis is hotly disputed.

His best known roles were that of Mephistopheles in Goethe's Faust in 1956/57, and as "Der Schränker" (The Safecracker) who is the chief judge of the kangaroo court presiding over Peter Lorre in Fritz Lang's M.