The occupation of Norway by Nazi Germany during the Second World War began on 9 April 1940 after Operation Weserübung. Conventional armed resistance to the German invasion ended on 10 June 1940, and Nazi Germany controlled Norway until the capitulation of German forces in Europe on 8 May 1945. Throughout this period, a pro-German government named Den nasjonale regjering ruled Norway, while the Norwegian king Haakon VII and the prewar government escaped to London, where they formed a government in exile. Civil rule was effectively assumed by the Reichskommissariat Norwegen, which acted in collaboration with the pro-German puppet government. This period of military occupation is, in Norway, referred to as the "war years", "occupation period" or simply "the war".

The Altmark incident was a naval incident of World War II between British destroyers and the German tanker Altmark, which happened on 16–17 February 1940. It took place in what were neutral Norwegian waters. On board the Altmark were roughly 300 Allied prisoners, whose ships had been sunk by the pocket battleship Graf Spee in the Southern Atlantic Ocean.