| Competition: | Irish Premier League |
| Season: | 2005–06 |
| Winners: | Linfield 46th Irish title |
| Relegated: | Institute Ards |
| Continentalcup1: | UEFA Champions League |
| Continentalcup1 Qualifiers: | Linfield |
| Continentalcup2: | UEFA Cup |
| Continentalcup2 Qualifiers: | Glentoran Portadown |
| Continentalcup3: | UEFA Intertoto Cup |
| Continentalcup3 Qualifiers: | Dungannon Swifts |
| Matches: | 240 |
| Prevseason: | 2004–05 |
| Nextseason: | 2006–07 |
The 2005–06 Irish Premier League was the 105th edition of the Irish League, the highest level of league competition in Northern Irish football, and the 3rd edition in its current format (as the Irish Premier League) since its inception in 2003. The league consisted of 16 teams, and Linfield won the championship.
Ards were relegated after finishing bottom of the table, and Institute were relegated after a 3-1 defeat on aggregate to Donegal Celtic in the promotion play-off.
Each team played every other team twice (home and away) for a total of 30 games.
Institute, the club that finished in the relegation play-off place, faced Donegal Celtic, the runners-up of the 2005–06 Irish First Division in a two-legged tie for a place in next season's Irish Premier League.
----Donegal Celtic won 3–1 on aggregate and were promoted, Institute were relegated.