Earls of Northumberland

The title of Earl of Northumberland was created several times in the Peerage of England and of Great Britain, succeeding the title Earl of Northumbria. Its most famous holders were the House of Percy (alias Perci), who were the most powerful noble family in Northern England for much of the Middle Ages. The heirs of the Percys, via a female line, were ultimately made Duke of Northumberland in 1766.

William de Percy, 1st Baron Percy, who came from the village of Percy in Normandy, was in the train of William I. After arriving in England following the Harrying of the North (1069–70), he was bestowed modest estates in Yorkshire by Hugh d'Avranches. However, by the reign of Henry II the family was represented by only an heiress, Agnes de Percy (d.1203) following the death of the third feudal baron. As her dowry contained the manor of Topcliffe in Yorkshire, Adeliza of Louvain, the widowed and remarried second wife of Henry I, arranged the marriage of Agnes with her own young half-brother, Joscelin of Louvain. After their wedding, the nobleman from the Duchy of Brabant in the Holy Roman Empire settled in England. He adopted the surname Percy and his descendants were later created Earls of Northumberland. The Percys' line would go on to play a large role in the history of both England and Scotland. As nearly every Percy was a Warden of the Marches, Scottish affairs were often of more concern than those in England.

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