Koji Alexander Murofushi (広治アレクサンダー室伏, Kōji Arekusandā Murofushi, born October 8, 1974, in Numazu, Shizuoka Prefecture) is a former Japanese-Romanian hammer thrower and sports scientist. He has been among the world elite since the 2001 World Championships, where he won the silver medal. He was the 2004 Olympic champion. In 2011, he was crowned world champion.
He scored gold medals at both the 2001 Goodwill Games and the 2001 East Asian Games – setting a Games record at the latter event. After the 2001 World Championships, he proceeded by winning the 2002 Asian Championships and Asian Games as well as a silver medal at the 2002 World Cup and a bronze medal at the 2003 World Championships. That year he threw 84.86 metres, which was the longest hammer throw in over ten years, putting Murofushi fourth on the all-time performer's list. Among the favorites at the 2004 Summer Olympics, he eventually won the gold medal after the disqualification of Adrián Annus.
In August of 2011, Murofushi won the gold medal at the world championships, making him the oldest winner of the men's hammer world title. He also won the International Fair Play award at the same world championships.
He competed at the 2012 Summer Olympics, winning the bronze medal.
Koji Murofushi comes from a hammer throwing family, as his father Shigenobu Murofushi is a former Olympian and held the Japanese record for 23 years until his son broke it, and his sister, Yuka Murofushi, throws both hammer and discus. Murofushi's mother, Serafina Moritz (born 1950) is Romanian. She was a javelin thrower for Romania, European Junior champion in 1968, and Romanian senior champion in 1970. She is now a glass painter, and lives in Toyota City, Aichi Prefecture. Thanks to his mother, Murofushi speaks Romanian.