Ireland, or Éire, is an island in the far West of Europe. Politically it is divided into four parts: the northern-most kingdom is Ulster, on the west coast Connacht, in the south Munster (not to be confused with the Holy Roman Empire state of Munster-Westphalia) and in the east is Manx-run Leinster. The official language of the entire island is Gaeilge which is related to Manx.
Inhabited since at least 10,000 BC Ireland was gradually settled by waves of Celts from continental Europe. The Greeks and Romans knew of its existence, the Romans never made an attempt to conquer the island, however. It received Christianity from the missionaries Palladius and Patrick in the mid-5th century and, to a large degree, re-exported monastic Christianity alongside Greek and Latin teachings during the Dark Ages. By 900 AD the island was divided into nine separate kingdoms with endemic warfare firmly entrenched between them. The idea that a 'High King' (ruling from the Hill of Tara) would exercise suzerainty appeared in the 8th century but in reality the vying kings rarely achieved the power to claim the title and even then, would barely be recognised by their peers.
Viking adventurers raided the coastal settlements from around AD 795, eventually settling and founding several of the larger modern-day cities of Leinster and Munster. Attempts by these newcomers to carve out a Norse kingdom in Ireland were rebuffed by the local kings and their attentions switched to alternately propping up or trying to conquer the Northumbrian Kingdom. The bloodbath following Eirik Bloodaxe's defeat at Haugar in 934, and the subsequent carve-up of Norway, increased the numbers of Norse settlers arriving in Ireland. However, Norse presence was largely restricted to Dyflin (or Dubhlinn). The kings of Hordaland slowly increased their influence over the Dyflin Norse and in 1103 Magnus II helped the Dyfliners defeat Munster, securing their continued independence (though they were savvy enough to maintain allegiance to Leinster).
Wessex had already turned its attentions to Ireland. With a re-conquest of Anglia out of the question Edmund II had personally led an invasion of Ireland in 1028 but barely escaped with his life after disastrous engagement at Aughrim. The long reign of Edgar II produced no less than six separate invasions of Ireland with middling results. Afterward, Wessex would alternate its activities between Ireland and Northern Francia. The intrusion of Wessexian and Norse influence radically redefined the relationships between the Irish kingdoms as the petty kings sought alliances and influence with their more powerful neighbours. Despite their other interests the Wessex kings were much better placed and by 1268 following the Treaty of Waterford what is now Munster and southern Leinster was essentially a patchwork of Wessex-run earldoms and land still nominally held by the kings of Leinster and Munster, whilst the Ui Neill kings in Meath virtually ran the remainder as a fief of Wessex.
The crown of (and what was left territorially) of Leinster was joined permanently to the Manx kingdom in 1273 following the marriage of the future Sigurd III and Princess Cacht. Man would subsequently come to dominate the politics of non-Wessex held Ireland as the Ui Neill hold was shattered and Connacht and Ulster staged a resurgence. The kings of Man would also hold the title of High King of Ireland from 1457. When Man and its Irish territory was inherited by Hordaland in 1521 the new rulers sought a more direct domination of the island, simultaneously seeking to impose Lutheranism. This would result ultimately in the Revolt of Leinster in 1564 and a resumption in general war on the island as Wessex sought to re-establish its lost territory and stand up for the Catholic faith. Broadly known the 'Long Irish-Wessex War' this would last for roughly 200 years, but for most of its nominal duration it was formed by long periods of low-level warfare between Wessexian free-booting and opportune counter-raids. Wessex, Hordaland, Scotland, Brittany-Maine and Gwynnedd used the Irish conflicts as an arena to settle scores with each other but also as a release valve for its nobility.
Famine would hit the ever-growing Irish population repeatedly and the two Great Famines of 1741-42 and 1845-49 proved utterly ruinous. It is reckoned that each of the Great Famines effectively reduced the island's population by a third, both in terms of actual deaths and/or emigration (mostly to Manx Lancashire or Scotland).
Ulster would benefit most from the Industrial Revolution, the city of Béal Feirste becoming a shipbuilding hub. Connacht remained mostly agricultural and suffered badly from depopulation in the 19th and 20th centuries which is only now stabilising. Munster too remained mostly agricultural but benefited from improving relations with Wessex, close ties with Brittany-Maine and a history of liberal-minded government.In 1921 the three kingdoms (and Scotland) signed the Eire Neutrality Pact officially pacifying the island. The pact was signed by the majority of major European nations. In the subsequent decades the three kingdoms have largely put aside any differences and are moving toward a federal-style polity. In 2010 a 'Oireachtas', with its seat roughly in the centre at Ros Comáin, was formed with oversight of transport and trade links between the three, Man having an advisorary seat at the council. A separate Bank of Éire was created at the same time to standardise the Irish Puint. All three kingdoms mint separate designs, however. The intention is that the executive powers of the individual kingdoms will be slowly moved to this chamber, a process which has been slow to move thanks to entrenched opposition from certain groups, especially from the Church.