Auschwitz concentration camp (German: Konzentrationslager Auschwitz) was a network of concentration and extermination camps built and operated by the Third Reich in Polish areas annexed by Nazi Germany during World War II. It was the largest of the Nazi concentration camps, consisting of Auschwitz I (the Stammlager or base camp); Auschwitz II–Birkenau (the Vernichtungslager or extermination camp); Auschwitz III–Monowitz, also known as Buna–Monowitz (a labor camp); and 45 satellite camps.

Auschwitz had for a long time been a German name for Oświęcim, the town by and around which the camps were located; the name "Auschwitz" was made the official name again by the Nazis after they invaded Poland in September 1939. Birkenau, the German translation of Brzezinka ("birch forest"), referred originally to a small Polish village that was destroyed by the Nazis to make way for the camp.

Auschwitz II–Birkenau was designated by Reichsführer-SS Heinrich Himmler, the Third Reich's Minister of the Interior, as the place of the "final solution of the Jewish question in Europe". From early 1942 until late 1944, transport trains delivered Jews to the camp's gas chambers from all over German-occupied Europe. The camp's first commandant, Rudolf Höss, testified after the war at the Nuremberg Trials that up to three million people had died there (2.5 million gassed, and 500,000 from disease and starvation). Today the accepted figure is 1.3 million, around 90 percent of them Jewish. Others deported to Auschwitz included 150,000 Poles, 23,000 Roma and Sinti, 15,000 Soviet prisoners of war, some 400 Jehovah's Witnesses and tens of thousands of people of diverse nationalities. Those not killed in the gas chambers died of starvation, forced labor, infectious diseases, individual executions, and medical experiments.