The Admiralty was the authority in the United Kingdom responsible for the command of the Royal Navy. Originally exercised by a single person, the office of Lord High Admiral was from the 18th century invariably put "in commission", and was exercised by a Board of Admiralty, officially known as The Commissioners for Exercising the Office of Lord High Admiral of the United Kingdom of Great Britain and Northern Ireland, &c. (alternatively of England, Great Britain or the United Kingdom of Great Britain and Ireland depending on the period).

In 1964 the functions of the Admiralty were transferred to a new Admiralty Board, which is a committee of the tri-service Defence Council of the United Kingdom and part of the Ministry of Defence. The new Admiralty Board meets only twice a year, and the day-to-day running of the Royal Navy is controlled by a Navy Board (not to be confused with the historical Navy Board described later in this article). It is now uncommon for the various authorities now in charge of the Royal Navy to be referred to simply as "The Admiralty."

The title of Lord High Admiral of the United Kingdom is now vested in the Sovereign. However, there continues to be a Vice Admiral and a Rear Admiral of the United Kingdom, both of which are honorary offices.