| Birth Date: | 25 February 1975 |
| Birth Place: | Kanagawa Prefecture, Japan[1] |
| Height: | 174cm |
| Weight: | 88kg |
| School: | Fujisawa Nichidai High School |
| University: | Yamanashi Gakuin University[2] |
| Ru Position: | Centre |
| Years1: | 1996-2008 |
| Apps1: | 5 |
| Points1: | 0 |
| Repyears1: | 1999 |
| Repcaps1: | 0 |
| Reppoints1: | 0 |
, sometimes translated erroneously as Jun Koga,[3] (born Kanagawa Prefecture, 25 February 1975) is a Japanese former rugby union player who played as Centre.
After his graduation from Yamanashi Gakuin University,[4] for whose rugby club he played, Koga joined Sanyo Wild Knights,[5] where he played throughout all of his career until his retirement in 2008.[6] He was also part of the 1999 Rugby World Cup squad, but he never had a cap for Japan.