Sachsenhausen/Oranienburg KZ brief und Postkarte 1940 (Sachsenhausen Camp Letter and postcard 1940)

Sachsenhausen ("Saxon's Houses", German pronunciation: [zaksənˈhaʊzən]) or Sachsenhausen-Oranienburg was a Nazi concentration camp in Oranienburg, Germany, used primarily for political prisoners from 1936 to the end of the Third Reich in May 1945. After World War II, when Oranienburg was in the Soviet Occupation Zone, the structure was used as an NKVD special camp until 1950 (See NKVD special camp Nr. 7),

The camp was established in 1936. It was located 35 kilometres (22 mi) north of Berlin, which gave it a primary position among the German concentration camps: the administrative centre of all concentration camps was located in Oranienburg, and Sachsenhausen became a training centre for Schutzstaffel (SS) officers (who would often be sent to oversee other camps afterwards). Executions took place at Sachsenhausen, especially of Soviet prisoners of war. During the earlier stages of the camp's existence the executions were done in a trench, either by shooting or by hanging. A large task force of prisoners was used from the camp to work in nearby brickworks to meet Albert Speer's vision of rebuilding Berlin.

Sachsenhausen was originally not intended as an extermination camp—instead, the systematic murder was conducted in camps to the east. In 1942 large numbers of Jewish inmates were relocated to Auschwitz.