Medieval Brittany

former European sovereign state 939–1547, then dukedom of the Kingdom of France

Cornouaille (; , ) is a historical region on the west coast of Brittany in West France. The name is cognate with Cornwall in neighbouring Great Britain. This can be explained by the settlement of Cornouaille by migrant princes from Cornwall who created an independent principality founded by Rivelen Mor Marthou, and the founding of the Bishopric of Cornouaille by ancient saints from Cornwall. Celtic Britons and the settlers in Brittany spoke a common language, which later evolved into Breton, Welsh and Cornish.

short-lived vassal-state of the Frankish Empire

French admiral

thumb|Modern flag of Poher. Poher is an ancient principality that emerged in the Early Middle Ages in Cornouaille in west-central Brittany. Its capital was the Gallo-Roman city of Vorgium, capital of the Osismii, which became Carhaix after the fall of the Roman Empire. Archaeological excavations scheduled since 1999 show that, even if the city lost its function as capital after the 4th century, it was nonetheless a stronghold and major strategic crossroads.

Flag of Brittany

Domnonée is the modern French form of Domnonia or Dumnonia (Latin for "Devon"; ), a historic kingdom in northern Armorica (modern Brittany). It was founded by British immigrants from Dumnonia in Sub-Roman Britain who fled the Saxon invasions of Britain in the early Middle Ages. Headed by the same ruling dynasty, Domnonée was at times separate from, and at other times united with, its British motherland, and the Latin name Domnonia was applied to both regions interchangeably. On the continent, Domnonée encompassed the areas of Trégor, Dol-de-Bretagne, Goélo, and Penthièvre.

Historic realm and county of Brittany, France