William Henry Cavendish Cavendish-Bentinck, 3rd Duke of Portland, (14 April 1738 – 30 October 1809) was a British Whig and Tory statesman and twice Prime Minister of the United Kingdom of Great Britain. After his first time as prime minister, the kingdom of Ireland joined Great Britain to form the United Kingdom of Great Britain and Ireland. In the new Parliament of the United Kingdom, he again became prime minister in 1807. 