In the history of Germany, the Ministry of the Reichswehr or Reich Ministry of Defence (German: Reichswehrministerium) was the defence ministry of the Weimar Republic and the early Third Reich. The 1919 Weimar Constitution provided for a unified, national ministry of defence to coordinate the new Reichswehr, and that ministry was set up in October 1919, from the existing Prussian War Ministry and Reichsmarineamt. It was based in the Bendlerblock building. The Wehrgesetz (Defence Law) of 21 May 1935 renamed it the Reichskriegsministerium (Reich Ministry of War), which was then abolished in 1938 and replaced with the Oberkommando der Wehrmacht.
Within the framework of the Gesetzes über die Bildung einer vorläufigen Reichswehr ("Law on the formation of a provisional national-army") of March 1919, the Reichspräsident was commander-in-chief of the armed forces, with the Reichswehrminister (Reich Minister of Defence) exercising command. These arrangements left out the Prussian armed forces, which remained under the command of the Prussian Minister of War. After the Weimar Constitution came into force, the war ministries of Bavaria, Saxony, Württemberg and Prussia were dissolved and command authority was concentrated in the hand of the national Reichswehrminister. Power of command for each branch was given to the head of the Army Command (Heeresleitung) and the head of the Naval Command (Marineleitung). The Ministeramt was established as a third office within the ministry in 1929, with the Ministeramt′s head acting as the Reichswehrminister′s political deputy. The general staff took over the role of the Truppenamt.