Joan Beaufort (c. 1377 – 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 de Roet.

[1] She married Ralph de Neville, 1st Earl of Westmorland and in her widowhood became a powerful landowner in the north of England.

She may have been born at Kettlethorpe in Lincolnshire, the seat of the Swynford family, or at Pleshey in Essex, the home of Joan Fitzalan, Countess of Hereford.

[2] In September 1396 she, together with her siblings, the children of John of Gaunt and Katherine Swynford, were legitimised by papal bull.

[2] The couple's primary residence was the ancient Neville seat of Raby Castle in the county of Durham.

[8][9][10] Joan and Ralph were granted numerous offices, lands, wardships and pensions under Henry IV.

[5][12] Joan Beaufort was the mother of Cecily, Duchess of York, and thus was a grandmother of kings Edward IV and Richard III.