The Ministry of the Reichswehr 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 of 21 May 1935 renamed it the Reich Ministry of War, which was then abolished in 1938 and replaced with the Oberkommando der Wehrmacht.

Reichswehr was the official name of the German armed forces during the Weimar Republic and the first years of the Third Reich. After Germany was defeated in World War I, the Imperial German Army was dissolved in order to be reshaped into a peacetime army. From it a provisional Reichswehr was formed in March 1919. Under the terms of the Treaty of Versailles, the rebuilt German Army was subject to severe limitations in size, structure and armament. The official formation of the Reichswehr took place on 1 January 1921 after the limitations had been met. The German armed forces kept the name Reichswehr until Adolf Hitler's 1935 proclamation of the "restoration of military sovereignty", at which point it became part of the new Wehrmacht.