Gneisenau was a German capital ship, alternatively described as a battleship and battlecruiser, in Nazi Germany's Kriegsmarine. She was the second vessel of her class, which included her sister ship, Scharnhorst. The ship was built at the Deutsche Werke dockyard in Kiel; she was laid down on 6 May 1935 and launched on 8 December 1936. Her outfitting was completed in May 1938: she was armed with a main battery of nine 28 cm (11 in) C/34 guns in three triple turrets. At one point after construction had started, a plan had been approved to replace these weapons with six 38 cm (15 in) SK C/34 guns in twin turrets, but when it was realized that this would involve a lot of redesign, that plan was abandoned, and construction continued with the originally planned lower-calibre guns. The upgrade had been intended to be completed in the winter of 1940–41, but instead, due to the outbreak of World War II, that work was stopped.

The Kriegsmarine was the navy of Nazi Germany from 1935 to 1945. It superseded the Imperial German Navy of the German Empire (1871–1918) and the inter-war Reichsmarine (1919–1935) of the Weimar Republic. The Kriegsmarine was one of three official branches, along with the Heer and the Luftwaffe, of the Wehrmacht, the German armed forces from 1935 to 1945.