Aiyo Maru was a 2,746-ton transport ship of the Imperial Japanese Army during World War II. She left Rabaul, New Britain on 1 March 1943, as part of Operation 81, carrying a cargo of 252 troops, equipment, fuel, landing craft and ammunition for Lae, New Guinea. The convoy was attacked by aircraft of the United States Army Air Forces and Royal Australian Air Force from 2 March 1943, known as the Battle of the Bismarck Sea. Aiyo Maru was bombed on 3 March and sank at 07°15'S., 148°30'E. Up to 323 soldiers and sailors were killed.