The Aoba Class (青葉型巡洋艦) were a class of two heavy cruisers launched and commissioned in 1926-1927. Originally laid down in 1924 with the idea of constructing them as the third and fourth vessels of the Furutaka Class, improvements in gun turret design on the same year (with the creation of the twin 20cm (8in) gun turrets) made it so these changes would effectively happen on Aoba and Kinugasa while retrofitting Furutaka and Kako would prove impossible due to having already been laid down in late 1922. Thus, Aoba and Kinugasa were built as a new, separate class.
Their initial armament consisted of 3 of the aforementioned turrets, 2 fore and 1 aft. The ship's superstructure was also different from their predecessors in order to fit the new fire control requirements of the twin turrets, and 12 cm (4.7 in)/45-cal high angle guns were fitted instead of 7.62 (3 in) guns.
The airplane takeoff platform which was located partially atop of the number 4 semi-turret was also replaced with a catapult fitted just fore of the No.3 twin turret; Aoba's was gunpowder-propelled, whereas Kinugasa's was a compressed-air unit. However, because they were built on the same hull as Furutaka and Kako, machinery and armor between both classes remained roughly the same.
Multiple modernizations were performed on the Aoba Class starting from the early 1930s as part of an extensive modernization program of the "A class" cruisers, which included the improvement of their anti-aircraft units for better aiming abilities, with Kinugasa being refitted with a gunpowder-propelled catapult akin to Aoba's.
They were briefly decomissionned in 1938 to undergo a major refit which included the replacement of the 20 cm (7.9 in) main battery with 8 in (203 mm)/50-cal Mark II guns alongside strengthening of AA armament with the addition of 4 twin sets of 25 mm machine guns and 2 twin 13.2 mm (0.52 in) machine guns. Torpedo armament was also changed from 6 pairs (3 on each side) of fixed torpedo tubes mounted on the middle deck to 2 quadruple mounts using the "Long Lance" torpedo located on the upper deck. To prevent stability issues caused by the increased tonnage of the ships post-modernization, supplementary bulges were added which simultaneously improved torpedo protection. They were recommissionned thereafter on 1940.
During the Pacific War, Aoba and Kinugasa served as part of CruDiv6, consisting of both the Furutaka and Aoba class cruisers, which participated in the Invasion of Guam . Kinugasa was sunk on November 14, 1942 during the Naval Battle of Guadalcanal while Aoba survived until the bombing of Kure, 28th July 1945, before being scrapped in 1946-47.
The Aoba class was subsequently followed by the Myoukou Class cruisers.