Theodor Arps (2 February 1884 in Garmisch-Partenkirchen — 28 April 1947) was a German naval officer, most recently Deputy Admiral in World War II, from 1940 to 1945 Judge at the Reichskriegsgericht.
Theodor Arps was most known for managing the German Naval Intelligence Service (German:Marinenachrichtendienst), the German naval intelligence organization from 1 October 1934 to 31 December 1939.
Arps time at the Marinenachrichtendienst was known for increased rearmament at the agency, a modernizing period, preparing and undertaking assurance testing on the Naval Enigma for secure message use cases (which was insecure), training and mobilization planning and an increasingly efficient and modern signal intelligence architecture that was the culmination of two decades of work during the interwar period.