Norway
From the 8th to the 10th century, the wider Scandinavian region was the source of Vikings. The looting of the monastery at Lindisfarne in Northeast England in 793 by Norse people has long been regarded as the event which marked the beginning of the Viking Age. This age was characterised by expansion and emigration by Viking seafarers. They colonised, raided, and traded in all parts of Europe. Norwegian Viking explorers first discovered Iceland by accident in the 9th century when heading for the Faroe Islands, and eventually came across Vinland, known today as Newfoundland, in Canada. The Vikings from Norway were most active in the northern and western British Isles and eastern North America isles.
Kingdom of Dublin
Vikings invaded the territory around Dublin in the 9th century, establishing the Norse Kingdom of Dublin, the earliest and longest-lasting Norse kingdom in Ireland. Its territory corresponded to most of present-day County Dublin. The Norse referred to the kingdom as "Dyflin", which is derived . The first reference to the Vikings comes from the "Annals of Ulster" and the first entry for 841 CE reads: "Pagans still on Lough Neagh". It is from this date onward that historians get references to ship fortresses or longphorts being established in Ireland. It may be safe to assume that the Vikings first over-wintered in 840–841 CE. The actual location of the longphort of Dublin is still a hotly debated issue. Norse rulers of Dublin were often co-kings, and occasionally also Kings of Jórvík in what is now Yorkshire. Under their rule, Dublin became the biggest slave port in Western Europe.