Province (pop., 2002 prelim.: 2,105,449), eastern Ireland. It covers an area of 7,645 sq mi (19,801 sq km). Its counties include Carlow, Dublin, Kildare, Kilkenny, Laoighis, Longford, Louth, Meath, Offaly, Westmeath, Wexford, and Wicklow. Its northern part, Meath, was once a separate kingdom. In the early Middle Ages, kings of Leinster fought constantly against the Uí Néill, the line of high kings whose capital was at Tara in Meath. In the late 15th and early 16th centuries, Leinster was virtually independent, under the earls of Kildare.
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In order of size:
In ancient times Leinster was occupied by five major Fir-Bolg tribes, of which the tribe of Laigin rose to dominance and gave Leinster its name. The Fir Bolg may be related to the Belgae, but this has not been firmly established. The tribes of Leinster were united by Úgaine Mor Hugony, The Great, who built the hill-fort of Ailinne Knochawlin, near Kilcullen, County Kildare. He is a likely, but uncertain candidate as the first historical King of Laigin (Leinster) in the 7th century BC. The "-ster" of the toponym comes from the Nordic S-genitive and the Irish tír, meaning country, as the Vikings dominated and held Dublin, Wexford and Waterford, among other times for a period of time (around 800 - 1000). Therefore Leinster breaks down as:
or "the country of the Laigin".
The kingdom of Laigin was re-founded circa 175/185 AD following a period of civil wars in Ireland by the legendary Cathair Mor.
In the fourth and fifth centuries, after Magnus Maximus left Britain with his legions, leaving a power vacuum, colonists from Laigin settled in North Wales, specifically in Anglesey, Carnarvonshire, and Denbighshire. In Wales some of the Leinster-Irish colonists left their name on the Llŷn peninsula, which derives its name from Laigin.
By the eighth century, Laigin , had split into two dynasties:
Northern Leinster dynasty: Murchad mac Brain (d. 727), King of Uí Dúnlainge, and joint leader of the Laigin
After the death of the last Kildare-based King of Laigin, Murchad Mac Dunlainge in 1042, the Kingship of Leinster reverted to the Uí Cheinnselaig sept based in the south east (southern dynasty) which comprise the later Kings of Leinster.
Today, made of twelve counties, it encompasses the old province of Mide (mostly now in modern-day County Meath and County Westmeath). Also in it are County Longford and the Annally and Lusmagh parishes of County Offaly, formerly of Connacht, and County Louth, formerly of Ulster. The borders were redrawn by Cromwell for administration and military reasons. The last major boundary changes occurred with the formation of County Wicklow (1603-1606), from lands in the north of Carlow (which previously extended to the sea) and most of southern Dublin.
Later minor changes dealt with "islands" of one county in another. By the late 18th century, Leinster looked as shown below.