Katsunari Takayama (高山 勝成, Takayama Katsunari; born May 12, 1983) is a Japanese professional boxer. He is a five-time mini-flyweight world champion, having held the WBC title in 2005, the IBF title twice between 2013 and 2015, and the WBO title twice between 2014 and 2017. He retired as a professional in 2017, as WBO world champion, to focus on participation in the 2020 Olympics, but returned in 2020 after failing to qualify.
Source: “Katsunari Takayama”, English Wikipedia (CC BY-SA 4.0), excerpt