The 1920–21 Irish Cup was the 41st edition of the Irish Cup, the premier knock-out cup competition in Irish football.
Glentoran won the tournament for the 3rd time, defeating Glenavon 2–0 in the final at Windsor Park.
[1][2] This was the final tournament organised on an all-Ireland basis as the partition of Ireland process began in May 1921, and the FAI Cup was subsequently founded as an equivalent cup competition for teams in Southern Ireland (present-day Republic of Ireland).
[3] 1Glenavon advanced into the final after Shelbourne refused to play on 17 March which was set as the semi-final replay date following the IFA decision that the replay, like the original game would be played in Belfast.