The Police Battalion 309 (Polizeibattalion 309) was a formation of the Order Police (uniformed police) during the Nazi era. During Operation Barbarossa, it was subordinated to the German Army's 221st Security Division and deployed in German-occupied areas, specifically the Army Group Centre Rear Area, of the Soviet Union, as part of Wehrmacht's security forces. Alongside detachments from the Einsatzgruppen and the SS Cavalry Brigade, it perpetrated mass murders and was responsible for large-scale crimes against humanity targeting civilian populations.