Auschwitz was the Nazi camp complex that included Auschwitz II-Birkenau, the largest killing center of the Holocaust.
The complex was established in occupied Poland and grew into a network of camps, subcamps, and industrial work sites. Auschwitz I served as the original concentration camp, while Auschwitz II-Birkenau became the principal site of mass killing using gas chambers and crematoria. Auschwitz III-Monowitz was a forced-labor camp associated with the complex.
Nazi authorities deported Jews from across German-occupied Europe to Auschwitz. Approximately 1.1 million people were murdered there, the great majority of them Jews. Others imprisoned or killed included Roma, Soviet prisoners of war, and Polish political prisoners.
The camp complex was liberated by Soviet forces on 27 January 1945. That date later became International Holocaust Remembrance Day. Auschwitz is sometimes used to mean only Birkenau, but historically the name refers to the wider camp complex as well.