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.
Elliot was elected to the Irish House of Commons in 1796 as a Member of Parliament for St Canice. At the 1798 election he was returned for both Carlow Borough and for St Canice, but chose to continue to sit for St Canice. He held that seat until the Parliament of Ireland was abolished at the end of 1800 by the Act of Union, when he did not initially have a seat in the new Parliament of the United Kingdom.
However, he was elected at an unopposed by-election in 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.
- Leigh Rayment's Historical List of MPs – Constituencies beginning with "P" (part 1)
- Stooks Smith, Henry. (1973) [1844-1850]. Craig, F. W. S. (ed.). The Parliaments of England (2nd ed.). Chichester: Parliamentary Research Services. p. 236. ISBN 0-900178-13-2.
- Leigh Rayment's historical List of Members of the Irish House of Commons. Cites: Johnston-Liik, Edith Mary (2002). The History of the Irish Parliament 1692-1800 (6 volumes). Ulster Historical Foundation.
- Brian M. Walker, ed. (1978). Parliamentary election results in Ireland 1801–1922. Dublin: Royal Irish Academy. p. 4. ISBN 0-901714-12-7.
- Leigh Rayment's Historical List of MPs – Constituencies beginning with "P" (part 2)
- "No. 15906". The London Gazette. 1 April 1806. p. 420.