2005–06 Irish Premier League
The Irish Premier League in season 2005–06 comprised 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.Promotion/relegation play-off
, the club that finished in the relegation play-off place, faced Donegal Celtic, the runners-up of the 2005-06 Intermediate League First Division in a two-legged tie for a place in next season's Irish Premier League.
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Donegal Celtic won 3–1 on aggregate and were promoted, Institute were relegated.
