Érainn in the context of "Múscraige"

The Kingdom of Munster (Irish: Ríocht Mhumhan) was a kingdom of Gaelic Ireland which existed in the south-west of the island from at least the 1st century BC until 1118. According to traditional Irish history found in the Annals of the Four Masters, the kingdom originated as the territory of the Clanna Dedad (sometimes known as the Dáirine), an Érainn tribe of Irish Gaels. Some of the early kings were prominent in the Red Branch Cycle such as Cú Roí and Conaire Mór. For a few centuries they were competitors for the High Kingship of Ireland, but ultimately lost out to the Connachta, descendants of Conn Cétchathach. The kingdom had different borders and internal divisions at different times during its history.

Major changes reshaped Munster in the 6th century, as the Corcu Loígde (ancestors of the Ó hEidirsceoil) fell from power. Osraige which had been brought under the control of Munster for two centuries was retaken by the Dál Birn (ancestors of the Mac Giolla Phádraig). Various subordinate groups, such as the Múscraige, switched their alliance and helped to bring the Eóganachta to power in Munster. For the next three centuries, various subgroups such as the Eóganacht Chaisil (ancestors of the Ó Súilleabháin and Mac Cárthaigh) and Eóganacht Glendamnach (ancestors of the Ó Caoimh) competed for control of Munster. Celtic Christian civilisation developed at this time and the Rock of Cashel became a seat of power. Two kings, Faílbe Flann mac Áedo Duib and Cathal mac Finguine, were able to raise Munster to the premier Irish kingdom for a time.

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 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.

Deda mac Sin (Deda, son of Sen) was a prehistoric king of the Érainn of Ireland, possibly of the 1st century BC. Variant forms or spellings include Ded, Dedu, Dedad, Degad, Dega, Dego, Deguth and Daig, with some of these occurring as genitives although usage is entirely unsystematic, besides the rare occurrence of the obvious genitive Dedaid.

He is the eponymous ancestor of the Clanna Dedad, and may also have been a King of Munster.

The Dáirine (Dáirinne, Dáirfine, Dáirfhine) were a people of early medieval Ireland, probably derived from or closely associated with the Darini of Ptolemy's 2nd century Geography. In historical times the Dáirine included the Corcu Loígde, the Uí Fidgenti and Uí Liatháin of Munster, as well as the Dál Fiatach of Ulster. The name Dáirine also sometimes referred to the Érainn.