William Pitt the Younger (28 May 1759 – 23 January 1806) was a British statesman, the youngest and last prime minister of Great Britain (before the Acts of Union 1800) and then first prime minister of the United Kingdom (of Great Britain and Ireland) as of January 1801. He left office in March 1801, but served as prime minister again from 1804 until his death in 1806. He was also Chancellor of the Exchequer for all of his time as prime minister. He is known as "Pitt the Younger" to distinguish him from his father, William Pitt, 1st Earl of Chatham, who had previously served as prime minister and is referred to as "William Pitt the Elder" (or "Chatham" by historians).