Theodor Duesterberg (October 19, 1875-November 4, 1949) was a leader of the Stahlhelm, Bund der Frontsoldaten in Germany prior to the Nazi seizure of power.

Born the son of an army surgeon in Darmstadt, Duesterberg entered the Prussian Army in 1893 after training in the cadet corps. In 1900, Duesterberg was part of the East Asian Expedition Corps that saw action in China during the Boxer Rebellion. Two years later, Duesterberg became an officer and held a variety of army commands prior to World War I. During the war, Duesterberg served in the Prussian War Ministry and eventually attained the rank of lieutenant colonel. Following the war, Duesterberg resigned from the army in protest over the Versailles Treaty, which Duesterberg viewed as being extremely unfair to Germany. Duesterberg subsequently decided to enter politics and joined the DNVP in 1919. After various disagreements with the party leadership, however, Duesterberg left the DNVP in 1923 and joined the nationalistic and pro-monarchy Stahlhelm, Bund der Frontsoldaten, which largely consisted of ex-servicemen disgruntled with the Weimar Republic. Duesterberg quickly moved through the party hierarchy and by 1924 was one of two of its federal leaders (the other being Franz Seldte ). Under Duesterberg’s leadership, the Stahlhelm became Germany’s largest Freikorps group.

In the late 1920s, Duesterberg allied the Stahlhelm with the Nazi Party and other right wing groups and actively protested in 1929 against the Young Plan. Two years later, Duesterberg merged the Stahlhelm with the Nazis, DNVP, and other right wing groups in order to form the Harzburger Front . The Harzburger Front attempted to bring about the downfall of Heinrich Brüning and the Weimar Republic, but it eventually dissolved due to Adolf Hitler’s unwillingness to subordinate the Nazi Party to such a vast right wing coalition on a long term basis. After the dissolution of the Harzburger Front, Duesterberg continued to lead the Stahlhelm and maintained the organization’s alliance with the DNVP. In 1932, Duesterberg was nominated by the Stahlhelm and DNVP to run for President of Germany, but the Nazis ultimately destroyed any chance Duesterberg had of gaining mass support from the German people when they revealed he had Jewish ancestory. This revelation caused Duesterberg to poll poorly in the first ballot of the election, and he eventually withdrew from the race. Ironically, Duesterberg was offered a position in Hitler’s cabinet when Hitler became Chancellor of Germany in 1933, but Duesterberg flatly refused the proposal. Franz Seldte, however, did enter Hitler’s cabinet, which undermined the Stahlhelm and Duesterberg’s authority over the organization, and thus he resigned his leadership position in 1933.

In 1934, Duesterberg was arrested by the Nazis during the Night of the Long Knives and sent to Dachau concentration camp, where he was briefly interned. After being released, Duesterberg drifted into obscurity. He was known to have had limited contacts with the anti-Nazi Carl Friedrich Goerdeler in 1943, but Duesterberg ultimately did not play any role in Goerdeler’s plots against Hitler. In 1949, Duesterberg wrote The Steel Helmet and Hitler, in which he defended his pre-war political career and the Stahlhelm and detailed the movement’s independence from the Nazi Party. A year later, Duesterberg died in Hameln.