The Nagato-class battleships (長門型戦艦, Nagato-gata senkan) were a pair of dreadnought battleships built for the Imperial Japanese Navy (IJN) towards the end of World War I, although they were not completed until after the war. The last of Japan's pre-Treaty capital ships, they were the first class to carry 41 cm (16.1 in) guns, the largest afloat and the first bigger than 15 inches (381 mm). Nagato, the lead ship of the class, frequently served as a flagship.