Karl Rudolf Werner Best (10 July 1903 – 23 June 1989) was a German Nazi, jurist, police chief, SS-Obergruppenführer, and Nazi Party leader and theoretician from Darmstadt. He was the first chief of Department 1 of the Gestapo, Nazi Germany's secret police, and initiated a registry of all Jews in Germany. As a deputy of SS-Obergruppenführer Reinhard Heydrich, he organized the World War II SS-Einsatzgruppen paramilitary death squads that were responsible for mass killings.