Ruaidrí Ua Conchobair
Ruaidrí Ua Conchobair (c. 1116–1198), anglicised Rory O'Conor, succeeded his father Tairrdelbach as king of Connacht in 1156 and was inaugurated High King of Ireland in 1166, the first to rule without opposition. He expelled Diarmait Mac Murchada, but the exiled king's Norman allies invaded from 1169.
He united the Irish kings, besieged Dublin in 1171 and won at Thurles, but could not stop the invasion. The 1175 Treaty of Windsor made him Henry II's subordinate king; he abdicated in 1183 and died in 1198, the last High King of Ireland.