Ecgfrith (c. 645–May 20, 685) was the King of Northumbria from 670 until his death. He ruled over Northumbria when it was at the height of its power, but his reign ended with a disastrous defeat in which he lost his life.
Ecgfrith was the son of his predecessor as king, Oswiu of Northumbria. Bede tells us, in his Historia ecclesiastica gentis Anglorum, that Ecgfrith was held as a hostage "at the court of Queen Cynwise in the province of the Mercians" at the time of Penda of Mercia's invasion of Northumbria in 654 or 655. Penda was, however, defeated and killed by the Northumbrians under Oswiu in the Battle of Winwaed, a victory which greatly enhanced Northumbrian power.
Ecgfrith was made king of Deira, a sub-kingdom of Northumbria, in 664, and he became king of Northumbria following his father's death on February 15, 670. He had married Æthelthryth, the daughter of Anna of East Anglia, in 660; however, she took the veil shortly after Ecgfrith's accession, a step which possibly led to his long quarrel with Wilfrid, the Archbishop of York. Ecgfrith married a second wife, Eormenburg, before 678, the year in which he expelled Wilfrid from his kingdom.
Early in his reign he defeated the Picts, who had risen in revolt, and created a new sub-kingdom in the north called Lothian. In 674, Ecgfrith defeated Wulfhere of Mercia and seized Lindsey. In 679, he fought a battle against the Mercians under Æthelred (who had married Ecgfrith's sister, Osthryth) on the river Trent. Ecgfrith's brother Ælfwine was killed in the battle, and the province of Lindsey was given up when peace was restored at the intervention of Theodore of Canterbury.
In 684 Ecgfrith sent an expedition to Ireland under his general Berht, which seems to have been unsuccessful in the sense that no Irish land was conquered by the Northumbrians. But the expedition was successful in that Ecgfrith's men did manage to seize a large number of slaves and made off with a significant amount of plunder. In 685, against the advice of Cuthbert, he led a force against the Picts, who were led by his cousin Bruide mac Bili, but was lured by a feigned flight into their mountain fastnesses and slain at Nechtansmere (probably near Dunnichen in Forfarshire but possibly near Dunachton in Invernessshire). This disastrous defeat severely weakened Northumbrian power in the north, and Bede dates the beginning of the decline of Northumbria from Ecgfrith's death. He was succeeded by his illegitimate half-brother, Aldfrith.
A popular legend concerning Ecgfrith's death at Nechtansmere has his queen touring the church at Carlisle with Cuthbert during the campaign, as she could not bear to stay behind at the royal quarters and sit patiently awaiting news of the battle's outcome. During the tour Cuthbert stopped, paused, and said to Eormenburg: "I have just had a vision of your husband's death. Return to your palace and escape with your children." Almost immediately, a messenger arrived from the field at Nechtansmere with the unfortunate news that Ecgfrith had been slain and his host routed.
As well as his military activities, Ecgfrith appears to have been the earliest Northumbrian king, and perhaps the earliest Anglo-Saxon king, to have issued the silver penny, which became the mainstay of English coinage for centuries aftewards. Earlier Anglo-Saxon coins had been made, but these were rare, the most common being gold shillings or thrymsas, copied from Roman models. The pennies, or sceattas, were thick, cast in moulds, perhaps copied from Merovingian coins, and issued on a large scale.