Tamanoumi Masahiro (??? ??, February 5, 1944 – October 11, 1971), was a sumo wrestler, born in Aichi, Japan.
He was the sport's 51st yokozuna.
Making his professional debut in 1959, he reached the top makuuchi division in 1964.
He won six tournament championships and was runner-up in 12 others.
Earlier in his career he also earned six special prizes and four gold stars.
He was promoted to yokozuna simultaneously with his friend and rival Kitanofuji in January 1970 and the two men represented the dawning of a new era after the dominance of Taiho.
He died suddenly in October 1971 after a delayed appendectomy.