1999–2000 Irish League

The 1999–2000 Irish League was the 99th edition of the Irish League, the highest level of league competition in Northern Irish football. The league consisted of 10 teams, and Linfield won the championship.

Promotion/relegation play-off
Cliftonville, who finished in the relegation play-off place, faced Ards, the 2nd-placed team in the First Division, in a two-legged tie for a place in next season's Irish League Premier Division.

Cliftonville won 3–0 on aggregate