Monarchy of Ireland

Monarchical systems of government have existed in Ireland from ancient times. This continued in all of Ireland until 1949, when the Republic of Ireland Act removed most of Ireland's residual ties to the British monarch. Northern Ireland, as part of the United Kingdom, remains under a monarchical system of government.

The office of High King of Ireland effectively ended with the Anglo-Norman invasion of Ireland (1169–1171) in which the island was declared a fief of the Holy See under the Lordship of the King of England. In practice, conquered territory was divided amongst various Anglo-Norman noble families who assumed title over both the land and the people with the prior Irish inhabitants being either displaced or subjugated under the previously alien system of serfdom. Though the revolutionary change in the status quo was undeniable, the Anglo-Norman invaders would fail to conquer many of the Gaelic kingdoms of Ireland, which continued to exist, often expanding for centuries after, however none could make any viable claims of High Kingship. This lasted until the Parliament of Ireland conferred the crown of Ireland upon King Henry VIII of England during the English Reformation. Henry initiated the Tudor conquest of Ireland which ended Gaelic political independence from the English monarch who now held the crowns of England and Ireland in a personal union.

The Union of the Crowns in 1603 expanded the personal union to include Scotland. The personal union between England and Scotland became a political union with the enactments of the Acts of Union 1707, which created the Kingdom of Great Britain. The crowns of Great Britain and Ireland remained in personal union until it was also ended by the Acts of Union 1800, which united Ireland and Great Britain into the United Kingdom of Great Britain and Ireland in January 1801.

In December 1922, most of Ireland seceded from the United Kingdom, becoming the Irish Free State; at the same time, the newly created Northern Ireland, which covered most of Ulster, remained part of the United Kingdom. As a dominion within the British Empire, the Free State legally retained the same person as monarch as the United Kingdom—which in 1927 changed its name to the United Kingdom of Great Britain and Northern Ireland. In 1937, the Free State adopted a new constitution that removed all mention of the monarchy. In April 1949, the former Free State, which covered most of Ireland, declared itself a republic, and withdrew from the Commonwealth of Nations; this left Northern Ireland as the only part of the island that retained a monarchical system.

Gaelic Ireland consisted of as few as five and as many as nine Primary kingdoms (Cúicide/Cóicide 'fifths') which were often subdivided into many minor smaller kingdoms (Tuatha, 'folkdoms'). The primary kingdoms were Ailech, Airgíalla, Connacht, Leinster, Mide, Osraige, Munster, Thomond and Ulster. Until the end of Gaelic Ireland they continued to fluctuate, expand and contract in size, as well as dissolving entirely or being amalgamated into new entities. The role of High King of Ireland was primarily titular and rarely (if ever) absolute. Gaelic Ireland was not ruled as a unitary state.

The names of Connacht, Ulster, Leinster and Munster are still in use, now applied to the four modern provinces of Ireland. The following is a list of the main Irish kingdoms and their kings:

Máire Herbert has noted that "Annal evidence from the late eighth century in Ireland suggests that the larger provincial kingships were already accruing power at the expense of smaller political units. Leading kings appear in public roles at church-state proclamations ... and at royal conferences with their peers." (2000, p. 62). Responding to the assumption of the title ri hErenn uile ("king of all Ireland") by Mael Sechlainn I in 862, she furthermore states that

the ninth-century assumption of the title of "ri Erenn" was a first step towards the definition of a national kingship and a territorially-based Irish realm. Yet change only gained ground after the stranglehold of Uí Néill power-structures was broken in the eleventh century. ... The renaming of a kingship ... engendered a new self-perception which shaped the future definition of a kingdom and of its subjects.