| Competition: | Cymru Alliance |
| Season: | 2005–06 |
| Winners: | Glantraeth |
| Relegated: | Holywell Town Halkyn United |
| Prevseason: | 2004–05 |
| Nextseason: | 2006–07 |
The 2005–06 Cymru Alliance was the sixteenth season of the Cymru Alliance after its establishment in 1990. The league was won by Glantraeth.