Altmark was a German oil tanker and supply vessel, one of five of a class built between 1937 and 1939. She is best known for her support of the German commerce raider and "pocket battleship" Admiral Graf Spee and her subsequent involvement in the "Altmark Incident". In 1940, she was renamed Uckermark and used as supply tanker for the battleships Scharnhorst and Gneisenau during Operation Berlin before sailing to Japan in September 1942 as a blockade breaker.