1989–90 League of Ireland First Division

The 1989–90 League of Ireland First Division season was the fifth season of the League of Ireland First Division.

Overview
The First Division was contested by 10 teams and Waterford United F.C. won the division.

First Division play-off
After Waterford United and Sligo Rovers finished level on points, a play-off was held to decide the overall title winners.

2nd leg
Waterford United won 2–1 on aggregate and were declared champions.