The entirety of Germany was occupied and administered by the Allies of World War II from the Berlin Declaration on 5 June 1945 to the establishment of West Germany on 23 May 1949. Unlike occupied Japan, Germany was stripped of its sovereignty and former state: after Nazi Germany surrendered on 8 May 1945, four countries representing the Allies asserted joint authority and sovereignty through the Allied Control Council (ACC). At first, Allied-occupied Germany was defined as all territories of Germany before the 1938 Nazi annexation of Austria; the Potsdam Agreement on 2 August 1945 defined the new eastern German border by giving Poland and the Soviet Union all regions of Germany east of the Oder–Neisse line and divided the remaining "Germany as a whole" into four occupation zones, each administered by one of the Allies.

Military occupation, also called belligerent occupation or simply occupation, is the temporary control exerted by a ruling power's military apparatus over a sovereign territory that is outside of the legal boundaries of that ruling power's own sovereign territory. The controlled territory is then known as the occupied territory, with the ruling power being the occupant. Occupation is distinguished from annexation and colonialism on the basis that it is a power structure that the ruling power intends to keep in place only temporarily. In many cases, the occupant may establish a military government to facilitate the administration of the occupied territory, though this is not a necessary precondition for occupation to take place.