Mogami (最上) was the lead ship in the four-vessel Mogami class of heavy cruisers in the Imperial Japanese Navy. She was named after the Mogami Riverin Tōhoku region of Japan. The Mogami-class ships were constructed as "light cruisers" (per the Washington Naval Treaty) with five triple 6.1-inch dual purpose guns. They were exceptionally large for light cruisers, and the barbettes for the main battery were designed for quick refitting with twin 8-inch guns. In 1937 all four ships were "converted" to heavy cruisers in this fashion.