The 3rd Duke of Devonshire.

William Cavendish, 3rd Duke of Devonshire, KG, PC (26 September 1698 – 5 December 1755) was a British nobleman and Whig politician, the son of William Cavendish, 2nd Duke of Devonshire and Lady Rachel Russell.

He married Catherine Hoskins (or Hoskyn) (d. 8 May 1777) on 27 March 1718. They had seven children:

• Lady Caroline Cavendish (22 May 1719 – 20 January 1760), married William Ponsonby, 2nd Earl of Bessborough and had issue
• William Cavendish, 4th Duke of Devonshire (1720 – 2 October 1764)
• Lord George Augustus Cavendish (d. 2 May 1794), died unmarried
• Lady Elizabeth Cavendish (bef. 1727–1796), married Hon. John Ponsonby and had issue
• Field Marshal Lord Frederick Cavendish (c. 1729 – 21 October 1803), died unmarried
• Lord John Cavendish (c. 1734–1796)
• Lady Rached Cavendish (d. 1805). Married Horatio Walpole, 1st Earl of Orford.

He was made a Privy Counsellor (P. C.) in 1731, and served as Lord Privy Seal from 1731 to 1733. He was invested as a Knight of the Garter (K.G.) in 1733. In 1739, he was enlisted as a founding governor for the new children's charity, the Foundling Hospital in London, which aimed to alleviate the problem of babies being abandoned by destitute mothers and ended up becoming a centre for British art and music.