Admiral of the Fleet Alfred Ernle Montacute Chatfield, 1st Baron Chatfield, was a Royal Navy officer. During the First World War he was present as Sir David Beatty's Flag-Captain at the Battle of Heligoland Bight in August 1914, at the Battle of Dogger Bank in January 1915 and at the Battle of Jutland in May 1916. After the war he became Commander-in-Chief, Atlantic Fleet and then Commander-in-Chief, Mediterranean Fleet before serving as First Sea Lord in the mid-1930s in which role he won arguments that the Royal Navy should have 70 cruisers rather than the 50 cruisers that had been agreed at the Naval Conference of 1930, that the battleship still had an important role to play despite the development of the bomber and that the Fleet Air Arm should be part of the Royal Navy rather than the Royal Air Force. He subsequently served as Minister for Coordination of Defence in the early years of the Second World War.

Admiral of the Fleet is a five-star naval officer rank and the highest rank of the Royal Navy, formally established in 1688. The five-star NATO rank code is OF-10, equivalent to a field marshal in the British Army or a Marshal of the Royal Air Force. Apart from honorary appointments, no new admirals of the fleet have been named since 1995, and no honorary appointments have been made since 2014.