Sachsenhausen or Sachsenhausen-Oranienburg was a Nazi concentration camp in Oranienburg, Germany, used primarily for political prisoners from 1936 to May, 1945. It was located 35 km north of the German capital of Berlin, which gave it a primary position among the German concentration camps: the administrative center of all concentration camps was located in Oranienburg, and Sachsenhausen became a training center for SS (Schutzstaffel) officers (who would often be sent to oversee other camps afterwards). On the front entrance gates to Sachsenhausen is the infamous slogan Arbeit Macht Frei (German: "Work will set you free"). About 200,000 people passed through Sachsenhausen between 1936 and 1945. Some 30,000 inmates died there from exhaustion, disease, malnutrition or pneumonia from the freezing winter cold. Many were executed or died as the result of brutal medical experimentation. On April 22, 1945, the camp's remaining 3,000 inmates, including 1,400 women were liberated by the Red Army and Polish 2nd Infantry Division.

Camp punishments could be harsh. Some would be required to assume the "Sachsenhausen salute" where a prisoner would squat with his arms outstretched in front. 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. 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. However the construction of a gas chamber and ovens by the camp commandant Anton Kaindl in March 1943, facilitated the means to kill larger numbers of prisoners. The chamber used liquid Zyclon B which was placed in small glass bottles into the ventilation system next to the door. The bottle was broken with a spike and the gas mixed with the air and was forced into the chamber.

Sachsenhausen was intended to set a standard for other concentration camps, both in its design and the treatment of prisoners. An industrial area, outside the western camp perimeter, contained SS workshops in which prisoners were forced to work; those unable to work had to stand to attention for the duration of the working day.

Sachsenhausen was the site of the largest counterfeiting operation ever. The Nazis forced inmate artisans to produce forged American and British currency, as part of a plan to undermine the British and United States' economies. Over one billion pounds in counterfeited banknotes was recovered. The Germans introduced fake British £5, £10, £20 and £50 notes into circulation in 1943: the Bank of England never found them. Plans had been made to drop British pounds over London by plane

With the advance of the Red Army in the spring of 1945, Sachsenhausen was prepared for evacuation. On April 20–21, the camp's SS staff ordered 33,000 inmates on a forced march northeast. Most of the prisoners were physically exhausted and thousands did not survive this death march; those who collapsed en route were shot by the SS. On April 22, 1945, the camp's remaining 3,000 inmates, including 1,400 women were liberated by the Red Army and Polish 2nd Infantry Division.