| Competition: | Irish League Premier Division |
| Season: | 1999–2000 |
| Winners: | Linfield 43rd Irish title |
| Relegated: | Lisburn Distillery |
| Matches: | 180 |
| Total Goals: | 516 |
| League Topscorer: | Vinny Arkins (29) |
| Prevseason: | 1998–99 |
| Nextseason: | 2000–01 |
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.
| Competition: | Irish League First Division |
| Winners: | Omagh Town |
| Promoted: | Omagh Town |
| Matches: | 180 |
| Total Goals: | 536 |
| Prevseason: | 1998–99 |
| Nextseason: | 2000–01 |
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