Arthur I was 4th Earl of Richmond and Duke of Brittany between 1196 and 1203. He was the posthumous son of Geoffrey II, Duke of Brittany, and Constance, Duchess of Brittany. His father, Geoffrey, was the son of Henry II, King of England.

The now-extinct title of Earl of Richmond was created many times in the Peerage of England. The earldom of Richmond was initially held by various Breton nobles; sometimes the holder was the Breton duke himself, including one member of the cadet branch of the French Capetian dynasty. The historical ties between the Duchy of Brittany and this English earldom were maintained ceremonially by the Breton dukes even after England ceased to recognize the Breton dukes as earls of England and those dukes rendered homage to the King of France, rather than the English crown. It was then held either by members of the English royal families of Plantagenet and Tudor, or English nobles closely associated with the English crown. It was eventually merged into the English crown during the reign of Henry VII of England and has been recreated as a Dukedom.