Sitric Cáech or Sihtric Cáech or Sigtrygg Gále,[nb 1] (Old Norse: Sigtryggr, Old English: Sihtric, died 927) was a Viking[nb 2] leader who ruled Dublin and then Viking Northumbria in the early 10th century. He was a grandson of Ímar and a member of the Uí Ímair. Sitric was most probably among those Vikings expelled from Dublin in 902, whereafter he may have ruled territory in the eastern Danelaw in England. In 917, he and his kinsman Ragnall ua Ímair sailed separate fleets to Ireland where they won several battles against local kings. Sitric successfully recaptured Dublin and established himself as king, while Ragnall returned to England to become King of Northumbria. In 919, Sitric won a victory at the Battle of Islandbridge over a coalition of local Irish kings who aimed to expel the Uí Ímair from Ireland. Six Irish kings were killed in the battle, including Niall Glúndub, overking of the Northern Uí Néill and High King of Ireland.[nb 3]
In 920 Sitric left Dublin for Northumbria, with his kinsman Gofraid ua Ímair succeeding him as king. That same year he led a raid on Davenport, Cheshire, perhaps as an act of defiance against Edward the Elder, King of the Anglo-Saxons. In 921 Ragnall ua Ímair died, with Sitric succeeding him as King of Northumbria. Though there are no written accounts of conflict, numismatic evidence suggests there was a Viking reconquest of a large part of Mercia in the following few years. An agreement of some sort between the Vikings of Northumbria and the Anglo-Saxons was achieved in 926 when Sitric married a sister of Æthelstan, perhaps Edith of Polesworth. Sitric also converted to Christianity, though this did not last long and he soon reverted to paganism. He died in 927 and was succeeded by his kinsman Gofraid ua Ímair. Sitric's son Gofraid later reigned as King of Dublin, his son Aralt as King of Limerick, and his son Amlaíb Cuarán as king of both Dublin and Northumbria.