The Heptarchy (from the Greek ἑπτά hepta, "seven" and ἄρχω arkho, "to rule") is a collective name applied to the Anglo-Saxon kingdoms of England during late antiquity and the early Middle Ages, conventionally identified as seven: East Anglia, Essex, Kent, Mercia, Northumbria, Sussex and Wessex. The Anglo-Saxon kingdoms eventually unified into the Kingdom of England.
The term has been in use since the 16th century, but the initial idea that there were seven Anglo-Saxon kingdoms is attributed to the English historian Henry of Huntingdon in the 12th century and was first used in his Historia Anglorum.
By convention, the Heptarchy lasted from the end of Roman rule in Britain in the 5th century, until most of the Anglo-Saxon kingdoms came under the overlordship of Egbert of Wessex in 829: a period of European history often referred to as the Early Middle Ages or, more controversially, as the Dark Ages.
Though heptarchy suggests the existence of seven kingdoms, the number fluctuated, as kings contended for supremacy at various times within the conventional period. In the late 6th century, the king of Kent was a prominent lord in the south; in the 7th century, the rulers of Northumbria and Wessex were powerful; in the 8th century, Mercia achieved hegemony over the other surviving kingdoms, particularly with "Offa the Great". Yet, as late as the reigns of Eadwig and Edgar (955–75), it was still possible to speak of separate kingdoms within the English population.