The 2021 All-Ireland Under-20 Football Championship was the fourth staging of the All-Ireland Under-20 Championship and the 58th staging overall of a Gaelic football championship for players between the minor and senior grades. The competition began on 1 July and ended on 15 August 2021.
The defending champion was Galway; however, the team was beaten by Mayo after a penalty shootout in the Connacht semi-final.
The final was played on 15 August 2021 at Croke Park in Dublin, between Offaly and Roscommon, in what was their first ever championship meeting. Offaly won the match by 1-14 to 1-11 to claim a second title and a first title since 1988.