| Competition: | Cymru Alliance |
| Season: | 2002–03 |
| Winners: | CPD Porthmadog |
| Prevseason: | 2001–02 |
| Nextseason: | 2003–04 |
The 2002–03 Cymru Alliance was the thirteenth season of the Cymru Alliance after its establishment in 1990. The league was won by CPD Porthmadog.