When did the Vikings arrive in Ireland?
History of Ireland (800–1169)
The first recorded Viking raid in Irish history occurred in AD 795 when Vikings, possibly from Norway[10] looted the island of Lambay.[note 4] This was followed by a raid on the coast of Brega in 798, and raids on the coast of Connacht in 807.[11] These early Viking raids were generally small in scale and quick.
Ingimundr (tenth century)
Although Ingimundr's settlement on the Wirral appears to be the only specifically documented migration in the wake of the events of 902, his adventure was almost certainly not unique. No doubt other middle-ranking Viking lords settled followers along in the Irish Sea region, in places such as Cumbria, Galloway, Lancashire, and Mann. Although the expulsion of 902 may have led to a brief abatement of violent Viking activity in Ireland, within two decades there was a remarkable resurgence of such activity, and Dublin itself was retaken and restored in 917.