Sir William St Quintin, 3rd Baronet (c. 1662 – 30 June 1723), of Harpham in Yorkshire, was an English merchant and Whig politician who sat in the House of Commons from 1695 to 1723. He held a succession of public offices. St Quintin was Mayor of Hull again in 1715. In 1717, he became Commissioner of the Alienation Office, and in 1720 he was appointed joint Vice-Treasurer, Receiver General and Paymaster of Ireland, offices he held until his death. He was also a member of the Privy Council of Ireland.