William Elliot (12 March 1766 – 26 October 1818) was an Irish politician who sat in the Irish House of Commons before its abolition. After the Act of Union he sat as a Whig in the House of Commons of the United Kingdom of Great Britain and Ireland. However, he was elected at an unopposed by-electionin March 1801 as MP for Portarlington, and held that seat until the 1802 general election, when he was returned to the House of Commons of the United Kingdom for the English borough of Peterborough. He held that seat until his death in October 1818, aged 52.