Musashimaru Koyo (武蔵丸 光洋, Musashimaru Kōyō, born May 2, 1971 as Fiamalu Penitani), is a former sumo wrestler. He was the second foreign-born wrestler in history to reach the rank of yokozuna. He won over 700 top division bouts and took twelve top division tournament championships during his career. Musashimaru's sheer 235 kg (518 lb) bulk combined with 1.92 m (6 ft 3 1⁄2 in) of height made him a formidable opponent, and he was remarkably consistent and injury-free for most of his career. An amiable personality, his fan base was helped by a surprising facial resemblance to Japanese warrior hero Saigō Takamori. He now works as a coach at Musashigawa stable and an executive manager at the Japan Sumo Association.
Fiamalu Penitani was born in American Samoa, the fourth son of a Tongan-German father and a Samoan-Portuguese mother. The family moved to Oahu, Hawaiʻi when he was ten years old. While attending Waianae High School in Waianae he played American football and was offered a scholarship to Pasadena City College, but he also had success in Greco-Roman wrestling, and his wrestling coach encouraged him to give sumo a try. He moved to Japan and joined former yokozuna Mienoumi's Musashigawa stable in June 1989, initially on a trial basis only. This proved to be successful and he formally made his professional debut that September, adopting the shikona or ring name of Musashimaru. He moved up the ranks quickly, becoming an elite sekitori wrestler in July 1991 upon promotion to the jūryō division. He reached the top makuuchi division just two tournaments later in November 1991. He made komusubi in May 1992 and sekiwake in July. After a superb 13-2 record and runner-up honours in November 1993, and a 12-3 score the following January, he was promoted to ōzeki alongside Takanonami.