Haguroyama Masaji (Japanese: 羽黒山 政司, November 18, 1914 – October 14, 1969) was a Japanese professional sumo wrestler from Nakanokuchi, Niigata. He was the sport's 36th yokozuna. He was a yokozuna for a period of twelve years and three months dating from his promotion to that rank in May 1941 until his retirement in September 1953, which was an all-time record until surpassed in 2019 by Hakuhō. During his career Haguroyama won seven top division championships and was runner-up on six other occasions. However, he was always in the shadow of yokozuna Futabayama, who came from the same stable. After his retirement he was the head coach of Tatsunami stable until his death in 1969.