Osberht (died 21 March 867) was king of Northumbria in the middle of the 9th century. Sources on Northumbrian history in this period are limited. Osberht's descent is not known and the dating of his reign is problematic. He became king after Æthelred son of Eanred was murdered, however the date of Æthelred's death is uncertain. Little is known of Osberht's reign; he was replaced as king by Ælla who is described in most sources as a tyrant, and not a rightful king: one source states that he was Osberht's brother.The Great Heathen Army marched on Northumbria in the late summer of 866, seizing York on 21 November 866. Several accounts of the battle on 21 March 867 tell us that Osberht and Ælla met their deaths at the hands of the Vikings. After this, the Vikings appointed one Ecgberht to rule Northumbria.