Sir William Hamilton, KB, PC, FRS, FRSE (13 December 1730 – 6 April 1803) was a British diplomat, politician, antiquarian and vulcanologist who served as the Envoy Extraordinary to the Kingdom of Naples from 1764 to 1800. After sitting in the House of Commons of Great Britain from 1761 to 1764, he began working as a diplomat, succeeding Sir James Gray as the British ambassador to the Kingdom of Naples. While in Italy, Hamilton became involved in studying local volcanoes and collecting antiquities, becoming a fellow of the Royal Society and being given the Copley Medal. His second wife was Emma Hamilton, who was famed as the mistress of Horatio Nelson, 1st Viscount Nelson.