Medieval Irish historical tradition held that Ireland had been ruled by an Ard Rí or High King 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 Geoffrey Keating's Foras Feasa ar Éirinn, purported to trace the line of High Kings. The corpus of early Irish law does not support the existence of such an institution, and scholars now believe it is a pseudohistorical construct of the eighth century AD, a projection into the distant past of a political entity which did not become a reality until the Normans. Rulers like Máel Sechnaill mac Máele Ruanaid declared themselves as King ofAll Ireland but such claims did not gain the political support of other kingdoms, the Norse and Norse-Gaels and was unable to maintain peace with his own Uí Néill kinsmen. The traditional list of High Kings of Ireland is thus a mixture of fact, legend, fiction, and propaganda. The individuals appearing prior to the fifth century AD are generally considered legendary, and the application of the title to individuals before the ninth century is considered anachronistic. The annalists frequently describe later high kings as rígh Érenn co fressabra, which is a reference to the instability of the kingship of Tara from the death of Máel Sechnaill mac Domnaill in 1022. Máel Sechnaill had been overthrown by Brian Boru in 1002, and restored in 1014 following Brian's death, but the example of Brian's coup was followed by numerous other families in the century following 1022, and the High Kingship was effectively ended by the Norman quasi-conquest of Ireland in 1171.
Legendary kings
Kings in the ''Baile Chuind''
The earliest surviving list appears in the Baile Chuind, a late seventh century poem in which Conn of the Hundred Battles experiences a vision of the kings who will succeed him. Many of these kings appear to correspond with the kings of later traditions, although the order is different, and some of the kings cannot be identified. The last four kings following Snechta Fína do not correspond with any of the kings in later lists. The poem is therefore presumed to have been written during his time, and the kings who follow him are presumed to be fictional. With few exceptions, kings belong to Dál Cuinn. Understood as a list of Kings of Tara, it is not considered to be inclusive. A number of well known kings from the Laigin, Érainn, Ulaid, and Cruthin, are missing. The chief rivals of Dál Cuinn at the time of Conn's supposed floruit were the Dáirine, alias Corcu Loígde, two of whom are listed, but whose overkingdom in the south of Ireland collapsed in the 7th century. They would be replaced by the Eóganachta, who established the Kingship of Cashel, later to rival Tara.
Synthetic lists
The Lebor Gabála Érenn, dating to the 11th–12th century, purports to list every High King from remote antiquity to the time of Henry II's Lordship of Ireland in 1171. The High Kingship is established by the Fir Bolg, and their nine kings are succeeded by a sequence of nine kings of the Tuatha Dé Danann, most if not all of whom are considered euhemeriseddeities. After the Milesian conquest the High Kingship is contested for centuries between the descendants of Eber Finn and Érimón, sons of Míl Espáine. The original compilation stopped at the reign of Tuathal Techtmar. The kings of the Goidelic dynasties established by Tuathal were added by other editors. Later editions of the Lebor Gabála tried to synchronise its chronology with dateable kings of Assyria, Persia, and Ptolemaic Egypt and Roman emperors. There are a handful of sources slightly predating the Lebor Gabála Érenn covering significant portions of essentially the same list of Milesian High Kings, starting with the Laud Synchronisms estimated to have been compiled ca. 1021. The oldest section of the Lebor Gabála Érenn "Roll of Kings" is taken from the poems of Gilla Cómáin mac Gilla Samthainde written c. 1072. Early modern works like the Annals of the Four Masters and Geoffrey Keating's Foras Feasa ar Éirinn continued this tradition based on later Irish annals. Keating's chronology, based on reign lengths, is longer than the synchronised chronology of the Lebor Gabála, and the Four Masters chronology is even longer.
LGE
: synchronised dates from Lebor Gabála Érenn
FFE: chronology based on reign-lengths given in Geoffrey Keating's Forus Feasa ar Erinn.
AFM': chronology from the Annals of the Four Masters.
Many of these kings are considered to be legendary. Dynastic affiliations are based on the genealogies of historical dynasties who claimed them as an ancestor.
These kings are historical figures for the most part, but naming them High Kings of Ireland may be anachronistic or inaccurate in certain cases. Their dynastic affiliations are also uncertain, as some may have been posthumously added to groups they did not belong to.
Historical High Kings of Ireland
These kings can be considered genuinely historical High Kings.
Later attempts at revival
Brian Ua Néill, as part of the mid thirteenth century revolts against Norman colonisation
