An Esquire of the Body was a personal attendant and courtier to the Kings of England during the Late Middle Ages and the early modern period. The Knight of the Body was a related position, apparently sometimes merely an "Esquire" who had been knighted, as many were. The distinction between the two roles is not entirely clear, and probably shifted over time. The positions also existed in some lesser courts, such as that of the Prince of Wales.

William FitzWilliam, 1st Earl of Southampton, KG was an English courtier and soldier. He was the third son of Sir Thomas FitzWilliam of Aldwark and Lady Lucy Neville, daughter of John Neville, 1st Marquess of Montagu.