| Birth Date: | 12 March 1931 |
| Birth Place: | Osaka Prefecture, Japan |
| Height: | 162 cm |
| Sport: | Weightlifting |
| Show-Medals: | yes |
Kenji Onuma (Japanese: 大沼 賢治, born 12 March 1931) is a Japanese retired lightweight weightlifter who won a silver medal at the 1958 Asian Games. In that same year, he set an unofficial world record in the clean and jerk. Onuma placed fourth in weightlifting in the 1956 Summer Olympics and competed in weightlifting in the 1960 Summer Olympics.