Aikoku Maru (愛国丸) was an armed merchant cruiser of the Imperial Japanese Navy in World War II.

She was designed to be a combined passenger liner / cargo vessel for the Osaka Shosen Lines's regularly scheduled services to South America.

On 31 December 1941, the reconnaissance floatplane from Aikoku Maru spotted the American freighter Malama (3,275 GWT) en route to Wellington.

The second floatplane reacquired SS Malama south of the Cook Islands on 2 January 1942, and after making a strafing attack, ordered the ship to stop.

[4] On 9 May, Aikoku Maru captured the Dutch tanker Genota (7,897 GWT) 480 miles (770 km) SSE of Diego Suarez, Madagascar.

[2] After repairs at Seletar Naval Base in Singapore, the floatplanes on Aikoku Maru were upgraded to two Aichi E13As, two dual Type 96 25 mm AT/AA Guns were added, and an additional 70 torpedoes were loaded.

From September, Aikoku Maru was assigned to the IJN 8th Fleet and tasked with transporting the IJA 38th Infantry Division to Rabaul for the reinforcement of Guadalcanal.

[2] On 11 November, the raiders attacked the Dutch tanker Ondina (6341 GWT), which was accompanied by the minesweeper HMIS Bengal, southwest of the Cocos Islands.

[6] From 16 December 1942, Aikoku Maru was reassigned back to the IJN 8th Fleet, primarily as a military transport to support New Guinea operations, and her aircraft were disembarked.

[2] On 10 July 1943, as part of a convoy including the aircraft carrier Un'yō, Aokoku Maru was attacked by the submarine USS Halibut 170 nautical miles (310 km; 200 mi) north of Truk, which fired six torpedoes.

[2] On 6 October, Aikoku Maru returned to Tamano for repairs and refitting with additional weaponry, which included two 152 mm guns and four twin-mount Type 96s.

On 21 January 1944, Aikoku Maru loaded the 629 men of the 66th Naval Guard Unit, with ammunition, supplies and construction materials.

After making an abortive run to Brown Island, she returned to Truk on 16 February to find that most of the capital ships had evacuated the base in anticipation of an impending American attack.

The wreck of Aikoku Maru is a popular scuba diving spot in the waters of Truk Lagoon, despite her depth of approximately 64 metres (210 ft).