The city was founded in 673 by Saint Ethelreda, daughter of King Anna. The foundation was the establishment of an abbey to the north of the village of Cratendune on the Isle of Ely. Its name is said to mean "island of eels", a reference to the creatures that were often caught in the local rivers for food.
The abbey was destroyed in 870 by Danish invaders and not rebuilt for over a hundred years. The site was one of the last holdouts in England to William I, Hereward the Wake not surrendering until 1071. The Cathedral Church of the Holy and Undivided Trinity of Ely was started by William I in 1083 and completed in 1351, despite the collapse of the main tower in 1322, which was rebuilt as a octagonal tower. The bishopric of Ely was founded in 1109, it covers 1507 miles² and holds 610,000 people (1995) and 341 churches. The city took part in the Peasants' Revolt of 1381.
The Isle of Ely consists of 238,048 statute acres. The Isle did not become part of Cambridgeshire until 1965.
Ely is on the River Great Ouse and was a significant port until the 18th century.
Oliver Cromwell is associated with the city.