William Elliot (12 March 1766 – 26 October 1818)^[1] 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^[2] 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.^[3] At the 1798 election he was returned for both Carlow and for St Canice, but chose to continue to sit for St Canice.^[3] He held that seat until the Parliament of Ireland was abolished at the end of 1800 by the Act of Union,^[3] 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^[4] in March 1801 as MP for Portarlington, and held that seat until the 1802 general election,^[5] when he was returned to the House of Commons of the United Kingdom for the English borough of Peterborough.^[2] He held that seat until his death in October 1818, aged 52.^[1]

He was sworn as a Privy Councillor in March 1806, in Dublin Castle,^[6] and appointed on 28 March as Chief Secretary for Ireland^[6] in the Ministry of All the Talents. He held that post until 1807.