is a Japanese former Grand Prix motorcycle road racer. His best seasons were in 2000, when he finished second in the 125cc world championship behind Roberto Locatelli and in 2001, when he finished second behind Manuel Poggiali. With his 6 Grand Prix victories in 2001, Ui tied a record set by Kenny Roberts in 1983 of most wins by a rider without winning a championship. He raced in Japan in 2007, winning the All Japan 250cc Road Race Championship.
() (Races in bold indicate pole position, races in italics indicate fastest lap)