Koki Mizuno (?? ??, Mizuno Koki, born 6 September 1985) is a Japanese football player who plays for SC Sagamihara in J3 League.Mizuno began his professional career with JEF United Chiba, with whom he won the J.League Cup in 2005 and 2006; he was named most valuable player of the 2006 competition.
His other former clubs include Ventforet Kofu, Kashiwa Reysol, and Scottish side Celtic.
Mizuno has 4 caps for the Japan national team, including two appearances as a substitute at the 2007 Asian Cup.
As a youth, Mizuno also appeared in the 2005 World Youth Championship as a member of the Japanese Under-20 team, scoring one goal.He is the cousin of Keita Suzuki, also a footballer.