Koji Seo (瀬尾 公治) is a Japanese manga creator from Shobara, Hiroshima, Japan.

He debuted in 1996 with the one-shot HALF & HALF in Magazine Fresh. His two hits, Suzuka and Cross Over, both mixed the genres of sports with high school romance. Suzuka focused on track and field while Cross Over used basketball.
He was an assistant to Tsukasa Ōshima, and respects Fujiko F. Fujio and Masahito Soda.
In 2009 he designed the High School Girl Kimchi for Hokubi Construction food company.

He has stated in an interview that he was a member of his high school's track and field team and that he loves to watch baseball both emphasized in his hit manga Suzuka.