William de Braose, 3rd Lord of Bramber was a 12th-century Marcher lord who secured a foundation for the dominant position later held by the Braose family in the Welsh Marches. In addition to the family's English holdings in Sussex and Devon, William had inherited Radnor and Builth, in Wales, from his father Philip. By his marriage he increased the Braose Welsh holdings to include Brecon and Abergavenny.

The House of Braose was a prominent family of Anglo-Norman nobles originating in Briouze, near Argentan, Orne, Normandy. Members of this family played a significant part in the Norman conquest of England and subsequent power struggles in England, Wales and Ireland in the 11th to 14th centuries.