The De-Schutzstaffel.ogg Schutzstaffel (help·info) (German for "Protective Squadron"), abbreviated SS- or Runic "SS" (Runic)- was a major Nazi organization under Adolf Hitler and the Nazi Party. The SS grew from a small paramilitary unit to a powerful force that served as the Führer's "Praetorian Guard," the Nazi Party's "Shield Squadron" and a force that, fielding almost a million men, (both on the front lines and as political police) managed to exert as much political influence as the Wehrmacht. Built upon the Nazi racial ideology, the SS, under Heinrich Himmler's command, was responsible for many of the crimes against humanity perpetrated by the Nazis during the World War II, and most of the worst of those crimes.

Initially numerically smaller than the Ernst Röhm's Sturmabteilung (Storm Battalion abbreviated SA), the SS grew in size and power due to its exclusive loyalty to Hitler, as opposed to the SA, which was seen as semi-independent and a threat to Hitler's hegemony over the party. Under Himmler, the SS selected its members according to the nazi racist ideology. Creating elite police and military units such as the Waffen-SS, Himmler used the SS to form an order of men claimed to be superior in racial purity and abilities to other Germans and national groups, a model for the Nazi vision of a master race. During World War II, SS units operated alongside the regular German Army, and in the final stages of the war, exercised dominance over it, to eliminate perceived threats to Hitler's power while implementing his strategies, despite the increasingly failing war effort.

The SS was responsible for the vast majority of war crimes perpetrated under the Nazi regime, including the Holocaust. As part of its race-centric functions, the SS oversaw the isolation and displacement of Jewish people from the populations of Germany and conquered territories, seizing their assets and imprisoning them in concentration camps and ghettos where they would be used as slave labor, pending extermination.

Chosen to implement the Nazi "Final Solution" for the Jews and other groups deemed "inferior," the SS carried out the enslavement, torture and killing of approximately twelve million people. Most victims were Jews and/or of Polish and Slavic extraction, but a significant number of victims included racial groups such as the Roma people. Furthermore the purge was extended to those viewed as deviant to the ideology of the master race including as per Nazi eugenics, not limited to but including political opponents, homosexuals, the mentally and physically disabled and handicapped. In addition those belonging to labour organisations and/or perceived to be affiliated with groups (religious, political, social and otherwise) that opposed the regime, or were seen to have views contradictory to the goals of the Nazi government were rounded up in large numbers including the clergy of all faiths, Jehovah's Witnesses, Freemasons, Communists, and Rotary Club members.

Foreseeing Nazi defeat in the war, a significant number of SS personnel organized their escape to South American nations. These escapes are said to have been assisted by an organisation known as ODESSA, an acronym of the German phrase Organisation der ehemaligen SS-Angehörigen, which translates as the Organization of Former Members of the SS. Many others were captured and prosecuted by Allied authorities at the Nuremberg Trials for war crimes, and absconding SS criminals were the targets of police forces in various Allied nations, post-war Germany, Austria and Israel.