OSWIO (c. 612-670)  , king of Northumbria, son of /Ethelfrith and brother of Oswald, whom he succeeded in Bernicia in 642 after the battle of Maserfeld, was the seventh of the great English kings enumerated by Bede . He succeeded in making the majority of the Britons, Picts and Scots tributary to .him . At Gilling in 651 he caused the murder of Oswine, a relative of Edwin, who had become king of Deira, and a few years later took possession of that kingdom . He appears to have consolidated his power by the aid of the Church and by a series of judicious matrimonial alliances . It was probably in 642 that he married Eanfied, daughter of Edwin, thus uniting the two rival dynasties of Northumbria . His daughter Alhfled he married to Peada, son of Penda, king of Mercia, while anotherdaughter, Osthryth, became the wife of /Ethelred, third son of the same king . Oswio was chiefly responsible for the reconversion of the East Saxons . He is said to have convinced their king Sigeberht of the truth of Christianity by his arguments, and at his request sent Cedd, a brother of Ceadda, on a mission to Essex . In 655 he was attacked by Penda, and, after an unsuccessful attempt to buy him off, defeated and slew the Mercian king at the battle of the Winwaed . He then took possession of part of Mercia, giving the rest to Peada . As a thank-offering he dedicated his daughter AElfled to the Church, and founded the monastery of Whitby . About this time he is thought by many to have obtained some footing in the kingdom of the Picts in succession to their king Talorcan, the son of his brother Eanfrid .

In 66o he married his son

Ecgfrith to /Ethelthryth, daughter of the East Anglian king Anna . In 664 at the synod of Whitby, Oswio accepted the usages of the Roman Church, which led to the departure of Colman and the appointment of Wilfrid as bishop of York . Oswio died in 67o and was succeeded by his son Ecgfrith . See Bede, Historia Ecclesiastica, ii., iii., iv., v., edited by C . Plummer (Oxford, 1896) ; Anglo-Saxon Chronicle, edited by Earle and Plummer (Oxford, 1899) .