Cornouaille ( or ) is a historic region of Brittany in northwest France. The name is cognate with the Cornwall region of Britain. This can be explained by settlement of Cornouaille by migrant princes from Cornwall creating an independent principality (during the Anglo-Saxon invasions) from (430–1084 AD) founded by Rivelen Mor Marthou, and the founding of the Bishopric of Cornouaille by ancient saints from the Cornwall region. The two regions spoke a similar Brythonic language which evolved into the Cornish language in Britain, and into a similar language, the Breton language across the English Channel in Brittany; both Breton and Cornish in turn are similar to Welsh.