The Chitose-class aircraft carriers (千歳型航空母艦, Chitose-gata kōkūbokan) were a class of two seaplane tenders, later converted to light aircraft carriers, of the Imperial Japanese Navy during World War II. Under the terms of the Washington Naval Treaty, the total tonnage of Japan's naval vessels was limited by class. The Chitose-class ships were built as seaplane tenders, designed to make the conversion to aircraft carriers relatively easy. They served as seaplane tenders during the early part of the Pacific War. After the Battle of Midway, they were converted into light aircraft carriers. Both ships participated in the Battle of the Philippine Sea and both were sunk in the Battle of Leyte Gulf.