Ragnall ua Ímair (Old Norse: Rǫgnvaldr [ˈrɔɣnˌwɑldz̠], died 921) or Rægnald was a Viking[nb 1] leader who ruled Northumbria and the Isle of Man in the early 10th century.
Ragnall was most probably among those Vikings expelled from Dublin in 902, whereafter he may have ruled territory in southern Scotland or the Isle of Man.
In 917, he and his kinsman Sitric Cáech sailed separate fleets to Ireland where they won several battles against local kings.
[3] Archaeological evidence suggests Dublin remained occupied in the years immediately following this expulsion, perhaps indicating only the ruling elite were forced to leave.
[7] According to Downham: "apart from these additions [of saga fragments], Irish chronicles are considered by scholars to be largely accurate records, albeit partisan in their presentation of events".
[12] The earliest mention of him in the Irish Annals is in 914 when he is described as defeating Bárid mac Oitir in a naval battle off the Isle of Man.
Niall Glúndub, overking of the Northern Uí Néill saw these Vikings as a threat, and he marched an army south to repel them.
The Vikings fought against the men of the Uí Néill at Mag Femen in County Tipperary and claimed victory, though only through timely reinforcement by Ragnall and his army.
[15] The Annals of Ulster record Ragnall, with his kinsman Gofraid and two earls, Ottir Iarla and Gragabai, leaving Ireland in 918 to fight against Constantín son of Áed, the king of Scotland.
According to the northern English historical tract Historia de Sancto Cuthberto (completed in the 11th century but probably with access to earlier material) Constantín was assisting Ealdred son of Eadwulf, ruler of all or some part of Northumbria.
This faction approached Æthelflæd, Lady of the Mercians, an Anglo-Saxon and a Christian, with an offer of submission, but negotiations were ended by her premature death in June 918.