Sōryū was an aircraft carrier built for the Imperial Japanese Navy (IJN) during the mid-1930s. A sister ship, Hiryū, was intended to follow Sōryū, but Hiryū's design was heavily modified and she is often considered to be a separate class. Sōryū's aircraft were employed in operations during the Second Sino-Japanese War in the late 1930s and supported the Japanese invasion of French Indochina in mid-1940. During the first months of the Pacific War, she took part in the attack on Pearl Harbor, the Battle of Wake Island, and supported the conquest of the Dutch East Indies. In February 1942, her aircraft bombed Darwin, Australia, and she continued on to assist in the Dutch East Indies campaign. In April, Sōryū's aircraft helped sink two British heavy cruisers and several merchant ships during the Indian Ocean raid.

Hiryū was an aircraft carrier built for the Imperial Japanese Navy (IJN) during the 1930s. Generally regarded as the only ship of her class, she was built to a modified Sōryū design. Her aircraft supported the Japanese invasion of French Indochina in mid-1940. She took part in the attack on Pearl Harbor and the Battle of Wake Island. During the first few months of the Pacific War, the ship supported the conquest of the Dutch East Indies in January 1942. The following month, her aircraft bombed Darwin, Australia; and continued to assist in the Dutch East Indies campaign. In April, Hiryū's aircraft helped sink two British heavy cruisers and several merchant ships during the Indian Ocean Raid.