| Koo Ji-won | |
| Birth Date: | 20 July 1994 |
| Birth Place: | Seoul, South Korea |
| Height: | 1.840NaN0 |
| Weight: | 1220NaN0 |
| Position: | Prop |
| Currentclub: | Kobelco Kobe Steelers |
| Years1: | 2017–2019 |
| Clubs1: | Sunwolves |
| Apps1: | 13 |
| Points1: | 0 |
| Years2: | 2018–2021 |
| Clubs2: | Mie Honda Heat |
| Apps2: | 14 |
| Points2: | 10 |
| Years3: | 2022– |
| Clubs3: | Kobelco Kobe Steelers |
| Apps3: | 10 |
| Points3: | 0 |
| Repyears1: | 2014 |
| Repteam1: | Japan U20 |
| Repcaps1: | 4 |
| Reppoints1: | 0 |
| Repyears2: | 2017– |
| Repteam2: | Japan |
| Repcaps2: | 25 |
| Reppoints2: | 0 |
| Repyears3: | 2023 |
| Repteam3: | Japan XV |
| Repcaps3: | 2 |
| Reppoints3: | 0 |
| Clubupdate: | 28 August 2023 |
| Repupdate: | 28 August 2023 |
is a Korean-Japanese professional rugby union player who plays as a prop for Japan Rugby League One club Kobelco Kobe Steelers. Born in South Korea, he represents Japan at international level after qualifying on residency grounds.[1] [2] [3] [4]
He also changed nationality to Japan after the 2019 World Cup
After only two Super Rugby appearances for the Sunwolves, which included one start, Koo received his first call-up to his adopted country, Japan's senior squad ahead of the 2017 end-of-year rugby union internationals.[5]