Heinrich Luitpold Himmler (German 7 October 1900 – 23 May 1945) was Reichsführer of the Schutzstaffel (Protection Squadron; SS), and a leading member of the Nazi Party (NSDAP) of Nazi Germany. Nazi leader Adolf Hitler briefly appointed him a military commander and later Commander of the Replacement (Home) Army and General Plenipotentiary for the administration of the entire Third Reich (Generalbevollmächtigter für die Verwaltung). Himmler was one of the most powerful men in Nazi Germany and one of the people most directly responsible for the Holocaust.

As a member of a reserve battalion during World War I, Himmler did not see active service. He studied agronomy in college, and joined the Nazi Party in 1923 and the SS in 1925. In 1929, he was appointed Reichsführer-SS by Hitler. Over the next 16 years, he developed the SS from a mere 290-man battalion into a million-strong paramilitary group, and, following Hitler's orders, set up and controlled the Nazi concentration camps. He was known to have good organisational skills and for selecting highly competent subordinates, such as Reinhard Heydrich in 1931. From 1943 onwards, he was both Chief of German Police and Minister of the Interior, overseeing all internal and external police and security forces, including the Gestapo (Secret State Police). Himmler had a lifelong interest in occultism, interpreting Germanic neopagan and Völkisch beliefs to promote the racial policy of Nazi Germany, and incorporating esoteric symbolism and rituals into the SS.

On Hitler's behalf, Himmler formed the Einsatzgruppen and built extermination camps. As facilitator and overseer of the concentration camps, Himmler directed the killing of some six million Jews, between 200,000 and 500,000 Romani people, and other victims; the total number of civilians killed by the regime is estimated at eleven to fourteen million people. Most of them were Polish and Soviet citizens.

Late in World War II, Hitler charged Himmler with the command of the Army Group Upper Rhine and the Army Group Vistula; he failed to achieve his assigned objectives and Hitler replaced him in these posts. Realising that the war was lost, he attempted to open peace talks with the western Allies without Hitler's knowledge shortly before the war ended. Hearing of this, Hitler dismissed him from all his posts in April 1945 and ordered his arrest. Himmler attempted to go into hiding, but was detained and then arrested by British forces once his identity became known. While in British custody, he committed suicide on 23 May 1945.