The III Army Corps / III AK (German: III. Armee-Korps) was a corps level command of the Prussian and then the Imperial German Armies from the 19th century to World War I. It was established in 1814 as the General Headquarters in Berlin (Generalkommando in Berlin) and became the III Army Corps on 3 April 1820. Its headquarters was in Berlin and its catchment area was the Province of Brandenburg.