Her Majesty's Most Honourable Privy Council is a group of advisors to Her Majesty the Queen. Most of the Queen's executive functions are exercised on the advice of the Privy Council. By constitutional convention, the only privy counsellors who may advise the Sovereign are those who are also ministers (and are therefore responsible to the elected House of Commons). These exercises of the Queen's functions, on the advice of the Privy Council, is referred to as the Queen-in-Council.

The Privy Council also exercises judicial functions (through its Judicial Committee) as a court of last appeal for some types of cases. Appeals are actually made to the Queen-in-Council, and are referred to the Privy Council for advice. The Privy Council accepts appeals under certain circumstances from the United Kingdom, and from several realms of the Commonwealth.