Sir William Wyndham, 3rd Baronet (c. 1688 – 17 June 1740), of Orchard Wyndham in Somerset, was an English Tory politician who sat in the House of Commons from 1710 to 1740. He served as Secretary at War in 1712 and Chancellor of the Exchequer in 1713 during the reign of the last Stuart monarch, Queen Anne (1702–1714). He was a Jacobite leader firmly opposed to the Hanoverian succession and was leader of the Tory opposition in the House of Commons during the reign of King George I (1714–1727) and during the early years of King George II (1727–1760).
His first wife was Lady Catherine Seymour, the younger of the two daughters of Charles Seymour, 6th Duke of Somerset (died 1748), and in her children by Wyndham, heiress to half of the vast estates, including Petworth House in Sussex and Egremont Castle in Cumberland, formerly held by the extinct Percy family, Earls of Northumberland. As a result of this complex inheritance his eldest son became the 2nd Earl of Egremont. Both his sons became earls and his daughter Elizabeth Wyndham was both the wife and mother of Prime Ministers, namely George Grenville and William Wyndham Grenville respectively.
