The 2021 All-Ireland Under-20 Hurling Championship was the third staging of the All-Ireland Under-20 Championship and the 58th staging overall of a hurling championship for players between the minor and senior grades. The championship began on 29 June 2021 and ended on 18 August 2021. The 2021 championship was the first to begin before the previous year's championship had concluded. Cork were the defending champions. The number of participating teams also increased, with Down and Kildare joining the Leinster Championship. Kildare's Liam Dempsey was the championship's top scorer with 0-37.