Koji Mise (Japanese: 三瀬 幸司, Hepburn: Mise Koji, born March 11, 1976) is a Japanese baseball player who played as a left-handed relief pitcher in Nippon Professional Baseball.

He was named the Pacific League's Rookie of the Year for 2004, with 55 appearances, throwing 67 and 2/3 innings, a 4-3-1 record and a 3.06 ERA with 28 saves.

He played as an outfielder in high school, but eventually switched to being a pitcher.

In college, he played on Okayama University of Science's team.

This biographical article relating to a Japanese baseball pitcher is a stub.