The Lord Privy Seal or Lord Keeper of the 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. The office is one of the traditional sinecure offices of state. Originally, its holder was responsible for the monarch's personal ("privy") seal (as opposed to the Great Seal of State, which is in the care of the Lord Chancellor). Today, the holder of the office is invariably given a seat in the Cabinet.

Though one of the oldest offices in government anywhere, it has no particular function today; thus the office has generally been used as a kind of Minister without Portfolio. Since the premiership of Clement Attlee, the position of Lord Privy Seal has frequently been combined with that of Leader of the House of Lords or Leader of the House of Commons. The jocular clarification that the office holder is neither a lord, nor a privy, nor a seal, though sometimes credited to Edward Heath, was attributed by him to Ernest Bevin.