Diarmait Mac Murchada, King of Leinster (born 1110)

Diarmait Mac Murchada, was King of Leinster in Ireland from 1127 to 1171. In 1167, he was deposed by the High King of Ireland, Ruaidrí Ua Conchobair. To recover his kingdom, Mac Murchada solicited help from King Henry II of England. His issue unresolved, he gained the military support of the Richard de Clare, 2nd Earl of Pembroke, thus initiating the Anglo-Norman invasion of Ireland.

The kings of Leinster ruled from the establishment of Leinster during the Irish Iron Age until the 17th century Early Modern Ireland. According to Gaelic traditional history found in works such as the Book of Invasions, Leinster was created during the division of Ireland among the Irish Gaels, descendants of Milesius: Leinster was one of the territories held by the offspring of Heremon. In the 7th century BC, the branch of the Heremonians who would establish Leinster, starting with Úgaine Mór, were also High Kings of Ireland and Kings of Tara. Their ascent to hegemony in Ireland was associated with the decline in influence of their Ulster-based Heremonian kinsmen from the Érainn.