The Holocaust: Nazi Germany carries out its final use of gas chambers to execute 33 Upper Austrian socialist and communist leaders in Mauthausen concentration camp.

The Holocaust, known in Hebrew as the Shoah, was the genocide of European Jews during World War II. From 1941 to 1945, Nazi Germany and its collaborators systematically murdered around six million Jews across German-occupied Europe, approximately two-thirds of Europe's Jewish population. The murders were committed primarily through mass shootings across Eastern Europe and poison gas chambers in extermination camps, chiefly Auschwitz-Birkenau, Treblinka, Belzec, Sobibor, Chełmno and Majdanek death camps in occupied Poland. Concurrent Nazi persecutions killed millions of other non-Jewish civilians and prisoners of war (POWs); the term Holocaust is sometimes used to include the murder and persecution of non-Jewish groups, such as the Romani and Soviet POWs.