The 1990–91 Irish Cup was the 111th edition of the Irish Cup, Northern Ireland's premier football knock-out cup competition. It concluded on 4 May 1991 with the final.
Glentoran were the defending champions after winning their 15th Irish Cup last season, defeating Portadown 3–0 in the 1990 final. This season Portadown went one better by winning their first Irish cup in their fifth appearance in the final. They defeated Glenavon 2–1 in the final.
Results First round The following teams were given byes into the second round: Ards Rangers, Armagh City, Ballymoney United, Crumlin United, Kilmore Rec., Limavady United, Magherafelt Sky Blues, Nitos Athletic, Portglenone, Rathfriland Rangers, Saintfield United, Sirocco Works and Star of the Sea.
Replays
Second round
Replays
Third round
Replay
Fourth round
Replays
Fifth round
Replays
Sixth round
Replays
Quarter-finals
Replay
Semi-finals
Final
References