Teiyō Maru was an auxiliary fleet oiler of the Imperial Japanese Navy (IJN) during World War II.

She was converted from civilian service to a naval auxiliary as the Pearl Harbor attack force sailed; and participated in the major offensive operations of the first six months of Pacific combat.

Teiyō Maru was then converted for cold weather operations and served for two years as a replenishment oiler for ships between Hokkaido and the Aleutian Islands.

The convoy sailed into the South China Sea from Mako naval base in the Pescadores on 17 August,[2] and was discovered that evening by USS Redfish.

Redfish assembled USS Rasher, Bluefish and Spadefish for a radar-assisted wolfpack attack in typhoon conditions on the night of 18/19 August.