Duke of Valois

The Valois, originally pagus valensis, was a region in the valley of the Oise river in Picardy in the north of France. It was a fief in West Francia and subsequently the Kingdom of France until its counts furnished a line of kings, House of Valois, to succeed the House of Capet in 1328. It was, along with the counties of Beauvais, the Vexin, Vermandois, and Laon, part of the "Oise line" of fiefdom which were held often by one individual or by an individual family as a string of defences against Viking assault on Paris.

The medieval county and duchy of Valois was located in northern France in northeastern Île-de-France. Its capital was Crépy-en-Valois.

to the royal domain by king Philip II

...
Wikipedia