Joan Beaufort, Countess of Westmorland, (c.1379 – 13 November 1440), was the fourth child (and only daughter) of John of Gaunt and his mistress Katherine Swynford. Joan married Robert Ferrers, 3rd Baron Ferrers of Wemme, and they had two daughters before he died. Along with her three brothers, Joan was privately declared legitimate by their cousin Richard II of England in 1390, but for some reason their father secured another such declaration from Parliament in January 1397. Perhaps the reason was that on 3 February 1397, when she was 18, Joan married Ralph Neville, 1st Earl of Westmorland, who had also been married once before. They had at least ten children, one of whom was Cecily Neville (1415–1495) ("Proud Cis"), who married Richard, Duke of York (1411–1460), and two of their children became Edward IV of England and Richard III of England.

Joan died on 13 November 1440 and was entombed next to her mother in the sanctuary of Lincoln Cathedral. Joan's is the smaller of the two tombs; both were decorated with brass plates — full-length representations of them on the tops, and small shields bearing coats of arms around the sides — but those were damaged or destroyed in 1644 during the English Civil War. A 1640 drawing of them survives, showing what the tombs looked like when they were intact, and side-by-side instead of end-to-end, as they are now.