Köln was a light cruiser, the third member of the that was operated between 1929 and March 1945, including service in World War II. She was operated by two German navies, the "Reichsmarine" and the "Kriegsmarine". She had two sister ships, and . "Köln" was built by the "Deutsche Werke" shipyard in Kiel; she was laid down in August 1926, launched in May 1928, and commissioned into the "Reichsmarine" in 15 January 1930. She was armed with a main battery of nine 15 cm SK C/25 (5.9-inch) guns in three triple turrets and had a top speed of .