Ruaidrí Ua Conchobair in the context of Anglicisation (linguistics)

Laudabiliter was a bull issued in 1155 by Pope Adrian IV, the only Englishman to have served in that office. Existence of the bull has been disputed by scholars over the centuries; no copy is extant but scholars cite the many references to it as early as the 13th century to support the validity of its existence. The bull grants the right to the Angevin King Henry II of England to invade and govern Ireland and to enforce the Gregorian Reforms on the semi-autonomous Christian Church in Ireland. Richard de Clare ("Strongbow") and the other leaders of the Anglo-Norman invasion of Ireland (1169–1171) claimed that Laudabiliter authorised the invasion. These Cambro-Norman knights were retained by Diarmait Mac Murchada, the deposed King of Leinster, as an ally in his fight with the High King of Ireland, Ruaidrí Ua Conchobair.

Successive kings of England, from Henry II (1171) until Henry VIII (1542), used the title Lord of Ireland and claimed that it had been conferred by Adrian's successor, Pope Alexander III (c. 1100/1105 – 1181).

Diarmait Mac Murchada (Modern Irish: Diarmaid Mac Murchadha; anglicised as Dermot MacMurrough or Dermot MacMurphy; c. 1110 – c. 1 May 1171), 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 (otherwise known as "Strongbow"), thus initiating the Anglo-Norman invasion of Ireland.

In exchange for his aid, Mac Murchada promised Strongbow the hand in marriage of his daughter Aoife and the right to succeed to the Kingship of Leinster. Henry II then mounted a larger second invasion in 1171 to ensure his control over Strongbow, resulting in the Norman Lordship of Ireland. Mac Murchada was later known as Diarmait na nGall (Irish for "Diarmait of the Foreigners"). He was seen in Irish history as the king that invited the first-ever wave of Anglo-Norman settlers, who were planted by the Norman conquest. The invasion had a great deal of impact on Irish Christianity, increasing the de facto ability of the Holy See to regulate Christianity in Ireland.

Aedh mac Ruaidrí Ua Conchobair was King of Connacht from 1228 to 1233. He was one of the sons of the last fully recognized High King of Ireland Ruaidrí Ua Conchobair, and claimed the kingship of Connacht after deposing his brother Toirdhealbhach Ó Conchobhair, after the death of their rival, cousin and former king Aedh Ua Conchobair. In 1233 he was killed in battle by the supporters of his cousin and successor Felim O'Connor. He was the last descendant of Ruaidrí to hold the kingship.

Medieval Irish historical tradition held that Ireland had a High King (Ard Rí) based at Tara since ancient times, and compilations like the 11th-century Lebor Gabála Érenn, followed by Early Modern works like the Annals of the Four Masters and Foras Feasa ar Éirinn, purported to trace the line of High Kings. John T. Koch explains: "Although the kingship of Tara was a special kingship whose occupants had aspirations towards supremacy among the kings of Ireland, in political terms it is unlikely that any king had sufficient authority to dominate the whole island before the 9th century". Máel Sechnaill I is often considered the first historical High King, although he faced some opposition. Applying the title to earlier kings is considered anachronistic, while kings from before the 5th century are generally considered legendary. The traditional list of High Kings is thus a mixture of historical facts and legend.

The annals describe some later High Kings as rígh Érenn co fressabra ("Kings of Ireland with opposition"), which is a reference to the instability of the kingship of Tara from the death of Máel Sechnaill mac Domnaill in 1022. He had been overthrown by Brian Boru in 1002, and restored in 1014 following Brian's death, but Brian's example was followed by many other dynasties in the century following 1022. The High Kingship was effectively ended in the 1170s after the Anglo-Norman invasion, its last holder being Ruaidrí Ua Conchobair.