Ecgfrith was the King of Deira from 664 until 670, and then King of Northumbria from 670 until his death in 20 May 685 possibly at age of 31. He ruled over Northumbria when it was at the height of its power, but his reign ended with a disastrous defeat at the Battle of Nechtansmere against the Picts of Fortriu in which he lost his life.

Deira was an area of Post-Roman Britain, and a later Anglian kingdom.