Mengele was born on 16 March 1911 to Walburga (née Hupfauer) and Karl Mengele in Günzburg, Bavaria, Germany. He was the oldest of three children; his two younger brothers were Karl Jr. and Alois. Their father was founder of the Karl Mengele & Sons company, producers of farm machinery. Josef was successful at school and developed an interest in music, art, and skiing. He completed high school in April 1930 and went on to study philosophy in Munich, where the headquarters of the Nazi Party were located. In 1931, Mengele joined the Stahlhelm, Bund der Frontsoldaten, a paramilitary organization that was absorbed into the Nazi Sturmabteilung (Storm Detachment; SA) in 1934.
In the autumn of 1941, SS chief Heinrich Himmler assigned German General Odilo Globocnik (SS and police leader for the Lublin District) with the implementation of a plan to systematically murder the Jews of the Generalgouvernement. The code name Operation Reinhard was eventually given to this plan, named after Heydrich (who was assassinated by Czech partisans in May 1942). As part of Operation Reinhard, Nazi leaders established three killing centers in Poland—Belzec, Sobibor, and Treblinka—with the sole purpose of the mass murder of Jews.
Mengele sailed to Argentina in July 1949, assisted by a network of former SS members. He initially lived in and around Buenos Aires, then fled to Paraguay in 1959 and Brazil in 1960, while being sought by West Germany, Israel, and Nazi hunters such as Simon Wiesenthal who wanted to bring him to trial. He eluded capture in spite of extradition requests by the West German government and clandestine operations by the Israeli intelligence agency Mossad. He drowned in 1979 after suffering a stroke while swimming off the Brazilian coast, and was buried under a false name. His remains were disinterred and positively identified by forensic examination in 1985.