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.

26 March 1921

Glentoran	2–0	Glenavon
Crooks Snape	Report

Windsor Park, Belfast

Referee: J. Sanderson

• Northern Ireland Cup Finals. Rec.Sport.Soccer Statistics Foundation (RSSSF)