A petty kingdom is one of a number of small kingdoms, described as minor or petty by contrast to an empire or unified kingdom that either preceded or succeeded it, e.g. the numerous kingdoms of Anglo-Saxon England and Dark Age Wales unified into the kingdom of England in the 10th century, or the numerous Gaelic kingdoms of Ireland unified as the Kingdom of Ireland in the 16th, or minor kingdoms in the immediate vicinity of larger kingdoms, such as the medieval Kingdom of Mann and the Isles relative to the kingdoms of Scotland or England.
In the context of the Dark Ages or the prehistoric Iron Age such minor kingdoms are also known as tribal kingdoms.
By the European High Middle Ages, many post-Roman Early Middle Ages petty kingdoms had evolved into principalities, grand duchies, or duchies. By the European Early Modern era many of these principalities had been mediated into larger monarchies, but the ruling families were considered morganatic for marriage considerations, and ranked equal to royal families in society.
The various small states of the Holy Roman Empire are generally not considered to be petty kingdoms since they were at least nominally subject to the Holy Roman Emperor and not fully independent.
Great Britain on the other hand has known many petty kingdoms. Listed below is a short overview of early medieval kingdoms.
Before the Kingdom of England was established as a united entity, there were various kingdoms in the area—of which the main seven were known as the heptarchy. These were Wessex, Mercia, Northumbria – also extended into present-day Scotland – East Anglia, Sussex, Kent, and Essex.