The 1991 All-Ireland Senior B Hurling Championship was the 18th staging of the All-Ireland Senior B Hurling Championship since its establishment by the Gaelic Athletic Association in 1974.

London entered the championship as the defending champions.

The All-Ireland final was played at Cusack Park in Mullingar on 7 July 1991 between Westmeath and London, in what was their third meeting in the All-Ireland final and a first meeting in seven years.

Westmeath won the match by 2-12 to 2-06 to claim their third All-Ireland title overall.

[1][2] Westmeath's David Kilcoyne was the championship's top scorer with 2-19.