William Pitt. William Pitt the Younger (28 May 1759?3 January 1806) was a British politician during the late eighteenth and early nineteenth centuries. He served as Prime Minister from 1783 to 1801, and again from 1804 until his death. He is known as William Pitt the Younger to distinguish him from his father, William Pitt the Elder, who also served as Prime Minister of Great Britain. The younger Pitt's prime ministerial tenure, which came during the reign of George III, was dominated by major events in Europe, including the French Revolution and the Napoleonic Wars. Pitt, a Tory, was both the youngest and one of the longest-serving Prime Ministers in British history.