The 1990 All-Ireland Under-21 Hurling Championship was the 27th staging of the All-Ireland Under-21 Hurling Championship since its establishment by the Gaelic Athletic Association in 1964. The championship began on 6 June 1990 ended on 9 September 1990.
Tipperary entered the championship as the defending champions.
On 9 September 1990, Kilkenny won the championship after a 2-11 to 1-11 defeat of Tipperary in the All-Ireland final. This was their fifth All-Ireland title overall and their first title since 1985.
Kilkenny's Jamesie Brennan was the championship's top scorer with 0-25.