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 River in Tōhoku region of Japan.
From 25 August, 1944, Mogami returned to Japan, and underwent a major conversion at Sasebo Naval Arsenal to an aircraft cruiser to improve the fleet's reconnaissance capabilities. Her No. 4 turret and the damaged No. 5 turret were removed and her aft magazines modified to serve as gasoline tanks and munitions storage. Her aft deck was extended and fitted with a rail system to accommodate the planned stowage of 11 Aichi E16A Zuiun (Paul) reconnaissance floatplanes.
Mogami served in numerous combat engagements in World War II (The Battle of Sunda Strait; Indian Ocean Raids; Battle of Midway; Battle of the Philippine Sea), until she was sunk at the Battle of Leyte Gulf in October 1944.