High Kings of Ireland in the context of "King of Leinster"

The history of Ireland 795–1169 covers the period in the history of Ireland from the first Viking raid to the Norman invasion. The first two centuries of this period are characterised by Viking raids and the subsequent Norse settlements along the coast. Viking ports were established at Dublin, Wexford, Waterford, Cork and Limerick, which became the first large towns in Ireland.

Ireland consisted of many semi-independent territories (túatha), and attempts were made by various factions to gain political control over the whole of the island. For the first two centuries of this period, this was mainly a rivalry between putative High Kings of Ireland from the northern and southern branches of the Uí Néill. The one who came closest to being de facto king over the whole of Ireland, however, was Brian Boru, the first high king in this period not belonging to the Uí Néill.

The kings of Leinster (Irish: Ríthe na Laighean) 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.

Apart from Úgaine Mór, other prominent Kings of Leinster from this period who were also High Kings of Ireland were Labraid Loingsech and Cathair Mór. A mythology developed that Labraid Loingsech had horses ears: he spent some time exiled in Transalpine Gaul (dated roughly to the period of the Roman–Gallic wars) where his grandmother was from and returned to Ireland with Gaullish mercenaries. He established a base in the area, which was renamed from "Gailian" to Leinster, in reference to the pointed-spears held by the Gaullish Gaesatae mercenaries who provided the backbone of Labraid Loingsech's powerbase and brought him to the High Kingship. Cathair Mór, who was also a High King of Ireland, is perhaps the most important figure genealogically in Leinster as all of the subsequent kinship groups which ruled Gaelic Leinster claimed descent and legitimacy to rule from one of his ten sons who had offspring.

The Hill of Tara (Irish: Teamhair or Cnoc na Teamhrach) is a hill and ancient ceremonial and burial site near Skryne in County Meath, Ireland. Tradition identifies the hill as the inauguration place and seat of the High Kings of Ireland; it also appears in Irish mythology. Tara consists of numerous monuments and earthworks—dating from the Neolithic to the Iron Age—including a passage tomb (the "Mound of the Hostages"), burial mounds, round enclosures, a standing stone (believed to be the Lia Fáil or "Stone of Destiny"), and a ceremonial avenue. There is also a church and graveyard on the hill. Tara forms part of a larger ancient landscape and Tara itself is a protected national monument under the care of the Office of Public Works, an agency of the Irish Government.

The term Kingship of Tara (/ˈtærə/) was a title of authority in ancient Ireland; the title is closely associated with the archaeological complex at the Hill of Tara. The position was considered to be of eminent authority in medieval Irish literature and Irish mythology, although national kingship was never a historical reality in early Ireland. The term also represented a prehistoric and mythical ideal of sacred kingship in Ireland. Holding the title King of Tara invested the incumbent with a powerful status. Many Irish High Kings were simultaneously Kings of Tara. The title emerged in the ninth and tenth centuries. In later times, actual claimants to this title used their position to promote themselves in status and fact to the High Kingship. Prior to this, various branches of the Uí Néill dynasty appear to have used it to denote overlordship of their kindred and realms. It was associated with Feis Temro (Feast of Tara), a pagan inauguration rite.

The titles King of Tara and High King of Ireland were distinct and unrelated for much of history.

The Kingdom of Leinster (Irish: Ríocht Laighean) was a kingdom of Gaelic Ireland which existed in the east of the island from the Irish Iron Age until the 17th century Early Modern Ireland. According to traditional Irish history found in the Annals of the Four Masters, the kingdom was founded as the territory of the Laighin, a Heremonian tribe of Irish Gaels. Some of the early kings of Leinster were also High Kings of Ireland and Kings of Tara, such as Úgaine Mór, Labraid Loingsech and Cathair Mór.

The Leinstermen had originally achieved hegemony in Ireland to the detriment of the Ulster-based Érainn, another group of Irish Gaels, but eventually lost out to their kinsmen the Connachta. This fall from power had lasting consequences in terms of territory for Leinster, as the Southern Uí Néill carved out the Kingdom of Meath to the north, and control of Osraige to the west was lost to the Corcu Loígde, becoming part of the Kingdom of Munster. The kingdom had different borders and internal divisions at different times during its history.

Tír Eoghain (meaning Land of Eoghan), also known as Tyrone, was a kingdom and later earldom of Gaelic Ireland, comprising parts of present-day County Tyrone, County Armagh, County Londonderry and County Donegal (Raphoe). The kingdom represented the core homeland of the Cenél nEógain people of the Northern Uí Néill and although they ruled, there were smaller groups of other Gaels in the area. One part of the realm to the north-east broke away and expanded, becoming Clandeboye, ruled by a scion branch of the O'Neill dynasty. In one form or another, Tyrone existed for over a millennium. Its main capital was Dungannon, though kings were inaugurated at Tullyhogue Fort.

Upon its foundation in the 5th century, Tyrone was a sub-kingdom of the larger Aileach, which represented the powerbase of the Uí Néill (descendants of Niall of the Nine Hostages) in the north of Ireland. The territory of Eoghan mac Néill was initially based in Inishowen and expanded out from there under his descendants. Periodically, during the time of Aileach, the leaders of Tyrone established themselves as High Kings of Ireland, providing in total of thirteen High Kings from the 6th to the 10th centuries. The first was Muirchertach mac Muiredaig and the last from this period was Domnall ua Néill. Three later Tyrone claimants to the High Kingship were Domnall Ua Lochlainn and Muirchertach Mac Lochlainn in 12th century and finally Brian Chatha an Dúna O'Neill in the 13th century.

The O'Neill dynasty (Irish: Ó Néill) are a lineage of Irish Gaelic origin that held prominent positions and titles in Ireland and elsewhere. As kings of Cenél nEógain, they were historically one of the most prominent family of the Northern Uí Néill, along with the O'Donnell dynasty. Some O'Neills state that their ancestors were kings of Ailech during the Early Middle Ages, as descendants of Niall of the Nine Hostages.

Two of their progenitors were High Kings of Ireland: Niall Glúndub (from whom they take their name) and Domnall ua Néill. From 1232 until 1616, the O'Neills were sovereign kings of Tír Eógain, holding territories in the north of Ireland in the province of Ulster, particularly around modern County Tyrone, County Londonderry and County Antrim, in what is now Northern Ireland. After their territory was merged with the Kingdom of Ireland and the land was caught up in the Plantation of Ulster, they were involved in a number of events, such as Tyrone's Rebellion, the Flight of the Earls, the Irish Rebellion of 1641 and the Irish Confederate Wars.