Kingdom of Dublin in the context of "Dublin"

Scandinavian York (Jórvík) or Viking York (Old Norse: Jórvík) is a term used by historians for what is now Yorkshire during the period of Scandinavian domination from late 9th century until it was annexed and integrated into England after the Norman Conquest; in particular, it is used to refer to York, the city controlled by these kings and earls. The Kingdom of Jórvík was closely associated with the longer-lived Kingdom of Dublin throughout this period.

The Viking Age (about 793–1066 CE) was the period during the Middle Ages when Norsemen known as Vikings undertook large-scale raiding, colonising, conquest, and trading throughout Europe and reached North America. The Viking Age applies not only to their homeland of Scandinavia but also to any place significantly settled by Scandinavians during the period. Although few of the Scandinavians of the Viking Age were Vikings in the sense of being engaged in piracy, they are often referred to as Vikings as well as Norsemen.

Voyaging by sea from their homelands in Denmark, Norway, and Sweden, the Norse people settled in the British Isles, Ireland, the Faroe Islands, Iceland, Greenland, Normandy, and the Baltic coast and along the Dnieper and Volga trade routes in eastern Europe, where they were also known as Varangians. They also briefly settled in Newfoundland, becoming the first Europeans to reach North America. The Norse-Gaels, Normans, Rus' people, Faroese, and Icelanders emerged from these Norse colonies. The Vikings founded several kingdoms and earldoms in Europe: the Kingdom of the Isles (Suðreyjar), Orkney (Norðreyjar), York (Jórvík) and the Danelaw (Danalǫg), Dublin (Dyflin), Normandy, and Kievan Rus' (Garðaríki). The Norse homelands were also unified into larger kingdoms during the Viking Age, and the short-lived North Sea Empire included large swathes of Scandinavia and Britain. In 1021, the Vikings achieved the feat of reaching North America—the date of which was not determined until a millennium later.

The Norse–Gaels (Old Irish: Gall-Goídil; Irish: Gall-Ghaeil; Scottish Gaelic: Gall-Gàidheal; Manx: Goal-Gael, 'foreigner-Gaels') were a people of mixed Gaelic and Norse ancestry and culture. They emerged in the Viking Age, when Vikings who settled in Ireland and in Scotland became Gaelicised and intermarried with Gaels. The Norse–Gaels dominated much of the Irish Sea and Scottish Sea regions from the 9th to 12th centuries. They founded the Kingdom of the Isles (which included the Hebrides and the Isle of Man), the Kingdom of Dublin, the Lordship of Galloway (which is named after them), and briefly ruled the Kingdom of York (939–944 AD). The most powerful Norse–Gaelic dynasty were the Uí Ímair or Ivar dynasty.

Over time, the Norse–Gaels became ever more Gaelicised and disappeared as a distinct group. However, they left a lasting influence, especially in the Isle of Man and Outer Hebrides, where most placenames are of Norse–Gaelic origin. Several Scottish clans have Norse–Gaelic roots, such as Clan MacDonald, Clan MacDougall and Clan MacLeod. The elite mercenary warriors known as the gallowglass (gallóglaigh) emerged from these Norse–Gaelic clans and became an important part of Irish warfare. The Viking longship also influenced the Gaelic birlinn and longa fada, which were used extensively until the 17th century. Norse–Gaelic surnames survive today and include MacIvor, MacAskill, and [Mac]Cotter.

Strathclyde (Welsh: Ystrad Clud, "valley of the Clyde"), also known as Cumbria, was a Brittonic kingdom in northern Britain during the Middle Ages. It comprised parts of what is now southern Scotland and North West England, a region the Welsh tribes referred to as Yr Hen Ogledd (“the Old North"). At its greatest extent in the 10th century, it stretched from Loch Lomond to the River Eamont at Penrith. Strathclyde seems to have been annexed by the Goidelic-speaking Kingdom of Alba in the 11th century, becoming part of the emerging Kingdom of Scotland.

In its early days it was called the kingdom of Alt Clud, the Brittonic name of its capital, and it controlled the region around Dumbarton Rock. This kingdom emerged during Britain's post-Roman period and may have been founded by the Damnonii people. After the sack of Dumbarton by a Viking army from Dublin in 870, the capital seems to have moved to Govan and the kingdom became known as Strathclyde. It expanded south to the Cumbrian Mountains, into the former lands of Rheged. The neighbouring Anglo-Saxons called this enlarged kingdom Cumbraland. We do not know what the inhabitants called their polity, though it may have been referred to as “Cumbria.”

The Uí Ímair (Irish: [iː ˈiːwəɾʲ] ; meaning ‘scions of Ivar’), also known as the Ivar dynasty or Ivarids, was a Norse-Gael dynasty which ruled much of the Irish Sea region, the Kingdom of Dublin, the western coast of Scotland, including the Hebrides and some part of Northern England, from the mid 9th century.

The dynasty lost control of York in the mid 10th century, but reigned over the other domains at variously disputed times, depending on which rulers may be counted among their descendants. This has proved a difficult question for scholars to determine, because reliable pedigrees do not survive. Additionally, for between three and four decades, the Uí Ímair were overkings of the Kingdom of Scotland itself, distinct from the Kingdom of Strathclyde, of which they may also have been overkings, and later briefly the Irish province of Munster, dominated from Waterford, and later still, briefly the English kingdom of Mercia. In the west of Ireland, the Uí Ímair also supplied at least two kings of Limerick, from which they may have attempted to conquer Munster again.