Lisbon Maru (りすぼん丸) was a Japanese cargo liner built at Yokohama in 1920 for a Japanese shipping line. During World War II, the ship was requisitioned by the Japanese Army and turned into an armed troopship. On her final voyage, Lisbon Maru was being used to transport prisoners of war between Hong Kong and Japan when it was torpedoed by the submarine USS Grouper on 1 October 1942. Over 800 British POWs died in the sinking, either by drowning or being shot by Japanese soldiers as they attempted to escape from the sinking ship. Approximately 380 British POWs were rescued by nearby Chinese fishermen, but were soon recaptured by the Japanese. The remaining 644 POWs were salvaged by nearby Japanese naval vessels from the water and taken back into captivity.