[1] The competition, which was delayed for a second successive year due to the impact of the COVID-19 pandemic on Gaelic games, began on 26 June 2021.

[2] Antrim, winner of the 2020 final, were promoted to the Leinster Senior Hurling Championship, while there was no relegation to or from the competition.

Down and Kildare entered the competition from the Christy Ring Cup.

[3] On 17 July 2021, Westmeath won the Joe McDonagh Cup after a 2-28 to 1-24 win over Kerry in the final at Croke Park.

Relegated from the All-Ireland Senior Hurling Championship Promoted from the Christy Ring Cup Promoted to the All-Ireland Senior Hurling Championship Relegated to the Christy Ring Cup Westmeath are promoted to the 2022 All-Ireland Senior Hurling Championship.