Sir William John Lyne KCMG was an Australian politician who served as Premier of New South Wales from 1899 to 1901, and later as a federal cabinet minister under Edmund Barton and Alfred Deakin. He is best known as the subject of the so called "Hopetoun Blunder", unexpectedly being asked to serve as the first Prime Minister of Australia but proving unable to form a government.

The premier of New South Wales is the head of government in the state of New South Wales, Australia. The Government of New South Wales follows the Westminster Parliamentary System, with a Parliament of New South Wales acting as the legislature. The premier is appointed by the Governor of New South Wales, and by modern convention holds office by their ability to command the support of a majority of members of the lower house of Parliament, the Legislative Assembly.