Joan Beaufort, Countess of Westmoreland
Joan Beaufort (c. 1379 – 13 November 1440), was the youngest of the four legitimised children and only daughter of John of Gaunt, 1st Duke of Lancaster (third surviving son of King Edward III), by his mistress, later wife, Katherine Swynford. She married Ralph de Neville, 1st Earl of Westmorland and in her widowhood became a powerful landowner in the North of England.