Arthur Karl Greiser (22 January 1897 – 21 July 1946) was a Nazi German politician, SS-Obergruppenführer and Reichsstatthalter (Reich Governor) 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.