| Koji Onuma | |
| Position: | Pitcher |
| Birth Date: | 3 July 1979 |
| Birth Place: | Higashiōsaka, Osaka, Japan |
| Bats: | Right |
| Throws: | Right |
| Debutdate: | May 6 |
| Debutyear: | 2001 |
| Debutteam: | Seibu Lions |
| Teams: | |
is a Nippon Professional Baseball pitcher for the Yokohama DeNA BayStars in Japan's Central League.