The Chatham ministry was a British government led by William Pitt, 1st Earl of Chatham that ruled between 1766 and 1768. Because of Pitt's former prominence before his title, it is sometimes referred to as the Pitt ministry. Unusually for a politician considered to be Prime Minister, Pitt was not First Lord of the Treasury during the administration, but instead held the post of Lord Privy Seal.

The Lord Privy Seal is the fifth of the Great Officers of State in the United Kingdom, ranking beneath the Lord President of the Council and above the Lord Great Chamberlain. Originally, its holder was responsible for the monarch's personal (privy) seal until the use of such a seal became obsolete. Though one of the oldest offices in European governments, it has no particular function today because the use of a privy seal has been obsolete for centuries; it may be regarded as a traditional sinecure, but today, the holder of the office is invariably given a seat in the Cabinet of the United Kingdom, and is sometimes referred to as a minister without portfolio.