Theodor August Konrad Loos (18 May 1883 – 27 June 1954) was a German actor.

[1] The son of a watchmaker and instruments manufacturer, he left secondary school prematurely and worked for three years at an export firm for music instruments in Leipzig, and after that for his uncle, an art dealer in Berlin.

In the 1930s he could be seen performing in classic theater, on over 400 occasions in Peer Gynt alone.

He remains perhaps best-known for his numerous roles in the films of Fritz Lang.

During the Third Reich Loos was a member of the Advisory Council (Präsidialrat) of the president of the Reichsfilmkammer.