The Mogami class (最上型) were four cruisers built for the Imperial Japanese Navy (IJN) during the 1930s. They were initially classified as light cruisers under the weight and armament restrictions of the London Naval Treaty. After Japan refused to comply any longer with that agreement, all four ships were rearmed with larger guns and were reclassified as heavy cruisers. All four fought in World War II and were sunk.The Mogamis have been seen by naval architects as a design failure.