King of Northumbria (c848-867)
Osberht became king around the year 848 by virtue of his ability to remove and kill his predecessor Aethelred. Despite ruling Northumbria for around 19 years little is known of his reign.
The Anglo-Saxon Chronicle tells us that he was deposed in 867, but not why. There is a story recorded in Geffrei Gaimar's Estoire des Engleisthat this was precipitated by the king's rape of the wife of a nobleman, Buern Bucecarle whilst he was away organising the coastal defences, and that Buern Bucecarle subsequently turned to the Danes (that is Vikings for assistance. Although whether there is any truth in this tale I do not know.
In any event Osberht was briefly replaced by Aelle in 867, until the appearance of the Viking 'Great Army' persuaded him to end his civil war with Aelle. Both kings combined forces to challenge the Viking forces occupying York and both died in the resulting defeat. The kingdom of Northumbria did not survive their deaths.
SOURCES
A Biographical Dictionary of Dark Age Britain by Ann Williams, Alfred P. Smyth and D. P. Kirby (Seaby 1991)
Historia regum Anglorum et Danorum by Simeon of Durham
The Anglo-Saxon Chronicles