Arthur Karl Greiser was a Nazi German politician, SS-Obergruppenführer, Gauleiter and Reichsstatthalter of the German-occupied territory of Wartheland. He was one of the persons primarily responsible for organizing the Holocaust in occupied Poland and numerous other crimes against humanity. He was arrested by the Americans in 1945, and was tried, convicted and executed by hanging in Poland in 1946 for his crimes, most notably genocide.