MV Nankai Maru was an 8,416-gross register ton (GRT) cargo ship built by Mitsubishi Shipbuilding & Engineering Company Ltd, Nagasaki, Japan, in 1933 for Osaka Shosen Kaisha.

She was part of the invasion fleet for the Midway operation in June 1942 and the Battle of Milne Bay in August–September 1942, where she was damaged by a bomb.

She was struck by a dud torpedo from the United States Navy submarine USS Kingfish on 8 December 1942 in the Philippine Sea near Okinotorishima.

On 25 December 1942, she was damaged by a torpedo from the submarine USS Seadragon in St. George's Channel near Cape St. George, New Ireland, and then collided with the Japanese destroyer Uzuki while Uzuki was maneuvering to counterattack Seadragon.

Nankai Maru was sunk during a voyage from Singapore by a torpedo from the submarine USS Sealion on 12 September 1944 in the South China Sea east of Hainan Island at 18°42′N 114°30′E / 18.700°N 114.500°E / 18.700; 114.500.