Heptarchy (Greek: ἑπτά; "seven" and ἀρχία; "sovereignty") is the name applied by historians to the period in English history after the Anglo-Saxon conquest of the southern portion of the island of Great Britain, named Angleland (England) by them, up to the time when the Vikings started their predations into parts of Britain.

This period is generally intended as covering the timespan from AD 500 to 850.

The word heptarchy refers to the existence (as was thought) of the seven kingdoms which eventually merged to become the Kingdom of England during the early 10th century, and comprised of Northumbria, Mercia, East Anglia, Essex, Kent, Sussex, and Wessex.

The term itself dates back to the twelfth century, and the English historian Henry of Huntingdon, and has been in common use since the sixteenth century.

More recent research has revealed that some of these kingdoms (notably Essex and Sussex) did not achieve the same status as did the others.

Conversely there also existed at the time a number of other political divisions which played a far more important role than was previously considered the case. Such were the kingdoms (or sub-kingdoms) of Lindsey (in present-day Lincolnshire), the Hwicce, the Magonsaete (in present-day Surrey), the Wihtware (from whence the Isle of Wight), the Middle Angles , the Haestingas (from whence Hastings in Sussex) and the Gewissae (which became the kingdom of Wessex).

Certainly the term Heptarchy has been considered unsatisfactory since the early twentieth century, and many historians have ceased using it, feeling it does not adequately describe the period to which it refers. However it remains in general use as a label of convenience for that period of English history.

Related terms: Bretwalda