Henry Addington, 1st Viscount Sidmouth, English politician, Prime Minister of the United Kingdom (d. 1844)
Henry Addington, 1st Viscount Sidmouth, (30 May 1757 – 15 February 1844) was a British Tory statesman who served as Prime Minister of the United Kingdom from 1801 to 1804.

Addington is best known for obtaining the Treaty of Amiens in 1802, an unfavourable peace with Napoleonic France which marked the end of the Second Coalition during the French Revolutionary Wars. When that treaty broke down he resumed the war, but he was without allies and conducted relatively weak defensive hostilities, ahead of what would become the War of the Third Coalition. He was forced from office in favour of William Pitt the Younger, who had preceded Addington as Prime Minister. Addington is also known for his reactionary crackdown on advocates of democratic reforms during a ten-year spell as Home Secretary from 1812 to 1822. He is the longest continuously serving holder of that office since it was created in 1782.