Earl of Northumbria or Ealdorman of Northumbria was a title in the late Anglo-Saxon, Anglo-Scandinavian and early Anglo-Norman period in England. The ealdordom was a successor of the Norse Kingdom of York.
In the seventh century, the Anglo-Saxon kingdoms of Bernicia and Deira were united in the Kingdom of Northumbria, but this was destroyed by the Vikings in 867. Southern Northumbria, the former Deira, then became the Viking kingdom of York, while the rulers of Bamburgh commanded territory to the North of the Tees, roughly equivalent to the northern kingdom of Bernicia. Scandinavian domination came to an end when Eadred's forces killed Eric Bloodaxe at the Battle of Stainmore in 954.
The whole area was then governed by earls, from the local nobility, who were appointed by the King of England to rule Northumbria in his stead. The honorific title "Earl" was Anglo-Scandinavian in origin. At the time of the Norman Conquest Northumbria was one of only seven Earldoms for all of England. The title of Earl was the highest rank below the king. In English counties Shire-Reeves would often govern a smaller area underneath the earl and where there was no earl in charge the king would appoint a Shire-Reeve to govern in his place.
In 1006 Uhtred the Bold, ruler of Bamburgh, by command of Æthelred the Unready became ealdorman in the south, temporarily re-uniting much of the area of Northumbria into a single jurisdiction. Uhtred was murdered in 1016, and Cnut then appointed Norwegian Eric of Hlathir to the Earldom of Northumbria, but Uhtred's dynasty held onto Bamburgh. Although a Scandinavian king ruled all of England, Northumbria was not well integrated into the rest of the country.
Siward became the last Scandinavian Earl of Northumbria when he succeeded Erik in about 1033. He governed for 22 years without difficulty. On Siward's death in 1055, the king of England, Edward the Confessor, chose a West Saxon to govern Yorkshire, in place of Siward's son, Waltheof. Edward's choice, Tostig Godwinson, was unpopular with locals. In 1065 Tostig was deposed by the northern nobility and replaced with Morcar (the brother of Edwin of Mercia). The northerners choice of new earl was accepted by Edward as well as by Tostig's brother Harold Godwinson.
After Edward the Confessor's death in 1066, Harold became King of England. In September 1066 Tostig, angry at Harold's betrayal, was back on the scene this time with his ally, Harald Hardrada of Norway. On 20 September 1066 the allies defeated, the northern earls, Morcar and Edwin at the Battle of Fulford although eventually they were defeated and killed, by Harold Godwinson, at the Battle of Stamford Bridge.
After the Norman Conquest the region was divided into multiple smaller baronies, one of which was the earldom of Northumberland, with others like the earldoms of York and numerous autonomous liberties such as the County Palatine of Durham and Liberty of Tynedale.