Admiral Sir David John Hallifax, KCB, KCVO, KBE (3 September 1927 – 23 August 1992) was a senior Royal Navy officer who served as Constable and Governor of Windsor Castle from 1988 until 1992.

Hallifax was educated at Winchester College, joined Britannia Royal Naval College, Dartmouth as a cadet in 1945^[1] and spent his early years in minesweepers based in the eastern Mediterranean. His first command was as a young lieutenant in the fast patrol boat MTB5008.

In 1954 Hallifax qualified as a Torpedo and Anti-Submarine Officer serving in HMS Salerno during the Suez Crisis in 1956 and later in HMS Whirlwind in the West Indies.^[2] He also commanded the destroyer HMS Agincourt^[1] at home and in East Asia before taking command of HMS Fife in 1973.^[1] Following an appointment to the Ministry of Defence as Director of Naval Operational Requirements, he became Flag Officer First Flotilla, a position once held by his father. It was from here that he went to the Northwood Headquarters as Chief of Staff to Admiral Sir John Fieldhouse, Commander-in-Chief Fleet in 1980.^[1] As Chief of Staff he was responsible for the day-to-day control of the Headquarters during the Falklands War. His next appointment was to the United States of America as the NATO Deputy Supreme Allied Commander Atlantic in 1982.^[1] His final appointment was Commandant of the Royal College of Defence Studies in 1986.^[1]

Hallifax retired from the navy on 1 March 1988.^[3] He was a keen yachtsman, competing in the 1971 Admirals Cup aboard the 'Prospect of Whitby'. He was a skilled woodworker, with a particular interest in fine reproduction furniture.^[1]

In February 1988 Hallifax was made Constable and Governor of Windsor Castle.^[4] He died of motor neurone disease in 1992.