Sachsenhausen or Sachsenhausen-Oranienburg was a German Nazi concentration camp in Oranienburg, Germany, used from 1936 until April 1945, shortly before the defeat of Nazi Germany in May later that year. It mainly held political prisoners throughout World War II. Prominent prisoners included Joseph Stalin's oldest son, Yakov Dzhugashvili; assassin Herschel Grynszpan; Paul Reynaud, the penultimate prime minister of the French Third Republic; Francisco Largo Caballero, prime minister of the Second Spanish Republic during the Spanish Civil War; the wife and children of the crown prince of Bavaria; Ukrainian nationalist leader Stepan Bandera; and several enemy soldiers and political dissidents.

From 1933 to 1945, Nazi Germany operated more than a thousand concentration camps, including subcamps on its own territory and in parts of German-occupied Europe.