William Pitt British Prime Minister (1759-1806) - William Pitt the Younger (28 May 1759 - 23 January 1806) was a British politician of the late eighteenth and early nineteenth centuries. He became the youngest-ever Prime Minister in 1783, aged 24. He left office in 1801, but was Prime Minister 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.