Theodor Eicke (17 October 1892 – 26 February 1943) was both a senior SS functionary and a Waffen-SS divisional commander in Nazi Germany. He was a key figure in the development of Nazi concentration camps. Eicke served as the second commandant of the Dachau concentration camp from June 1933 to July 1934, and together with his adjutant Michael Lippert, was one of the executioners of SA Chief Ernst Röhm during the Night of the Long Knives purge of 1934. He continued to expand and develop the concentration camp system as the first Concentration Camps Inspector.

In 1939, Eicke became commander of the SS Division Totenkopf of the Waffen-SS, leading the division during the Second World War on the Western and Eastern fronts. Eicke was killed on 26 February 1943, when his plane was shot down during the Third Battle of Kharkov.

Theodor Eicke was born on 17 October 1892, in Hampont (renamed Hudingen in 1915) near Château-Salins, then in the German Reichsland (province) of Elsass-Lothringen, the youngest of 11 children of a lower middle-class family. His father was a station master described as a German patriot. Eicke was an underachiever in school, dropping out at the age of 17 before graduation. Instead he joined the Bavarian Army (23rd Bavarian Infantry Regiment at Landau) as a volunteer, and then was transferred to the Bavarian 3rd Infantry Regiment in 1913.

Upon the start of First World War in 1914, Eicke participated in the Lorraine campaign, fighting at both the First Battle of Ypres in 1914 and the Second Battle of Ypres in 1915, and was with the 2nd Bavarian Foot Artillery Regiment at the Battle of Verdun in 1916. Eicke served as a clerk, an assistant paymaster, and a front-line infantryman, and for his bravery during the war was awarded the Iron Cross Second Class. Despite being decorated, Eicke spent most of the conflict behind the lines as a regimental paymaster.

Late in 1914, Eicke's commander had approved his request to temporarily return home on leave to marry Bertha Schwebel of Ilmenau on 26 December 1914, with whom he had two children: a daughter, Irma, on 5 April 1916 and a son, Hermann, on 4 May 1920.

Following the end of the First World War, Eicke remained as an army paymaster now in service of the Reichswehr of the Weimar Republic, until resigning from the position in 1919. Eicke began studying at a technical school in Ilmenau, but was forced to drop out shortly due to a lack of funds. From 1920, Eicke pursued a career as a police officer working for two different departments, initially as an informant and later as a regular policeman. Eicke's police career was ended in 1923 due to his open hatred for the Weimar Republic and his repeated participation in violent political demonstrations. He found work in 1923 at IG Farben in Ludwigshafen and remained there as a "security officer" until 1932.

Eicke's views on the Weimar Republic mirrored those of the Nazi Party, which he joined as member number 114,901 on 1 December 1928; he also joined the Sturmabteilung (SA), the Nazi Party's paramilitary street organization led by Ernst Röhm. Eicke left the SA by August 1930 to join the Schutzstaffel (SS) as member number 2,921, where he quickly rose in rank after recruiting new members and building up the SS organization in the Bavarian Palatinate. In 1931, Eicke was promoted to the rank of SS-Standartenführer (equivalent to colonel) by Heinrich Himmler, the Reichsführer of the SS.

In early 1932, his political activities caught the attention of his employer IG Farben, who subsequently terminated his employment. At the same time, he was caught preparing bomb attacks on political enemies in Bavaria for which he received a two-year prison sentence in July 1932. However, due to protection received from the Bavarian Minister of Justice Franz Gürtner, a Nazi sympathizer who would later serve as minister of justice under Adolf Hitler, Eicke was able to avoid his sentence and flee to Italy on orders from Heinrich Himmler. Italy at the time was already a fascist state under the rule of Benito Mussolini, and Eicke was entrusted by Himmler with running a "terrorist training camp for Austrian Nazis" at Lake Garda, and once even had the privilege of "showing Italian dictator Benito Mussolini around." On 28 October 1932, he officially met with Italian Fascists in the occasion of the tenth anniversary of the March on Rome, at the newly erected Bolzano Victory Monument.