The Principality or Kingdom of Gwynedd (Medieval Latin: Venedotia or Norwallia; Middle Welsh: Guynet,[4]) was one of several successor states to the Roman Empire that emerged in sub-Roman Britain in the 5th century during the Anglo-Saxon settlement of Britain.
Based in northwest Wales, the rulers of Gwynedd repeatedly rose to preeminence and were acclaimed as "King of the Britons" before losing their power in civil wars or invasions. The unitary kingdom of the Gruffydd ap Llywelyn was shattered by a Saxon invasion in 1063 just prior to the Norman invasion of Wales, but the House of Aberffraw restored by Gruffudd ap Cynan slowly recovered until Llywelyn the Great of Gwynedd was able to proclaim the Principality of Wales at the Aberdyfi in 1216. That realm lasted until the conquest of Wales by Edward I in 1283.
Welsh tradition credited the founding of Gwynedd to the Brittonic polity of Gododdin (Old Welsh Guotodin, earlier Brittonic form Votadini) from Lothian invading the lands of the Brittonic polities of the Deceangli, Ordovices, and Gangani in the 5th century.[5] The sons of their leader, Cunedda, were said to have possessed the land between the rivers Dee and Teifi.[6] The true borders of the realm varied over time, but Gwynedd Proper was generally thought to comprise the cantrefs of Aberffraw, Cemais, and Cantref Rhosyr on Anglesey and Arllechwedd, Arfon, Dunoding, Dyffryn Clwyd, Llŷn, Rhos, Rhufoniog, and Tegeingl at the mountainous mainland region of Snowdonia opposite. The modern preserved county of Gwynedd and principal area of Gwynedd are both somewhat smaller.