The Fourth Sea Lord and Chief of Naval Supplies originally known as the Fourth Naval Lord was formerly one of the Naval Lords and members of the Board of Admiralty which controlled the Royal Navy of the United Kingdom the post is currently known as Chief of Materiel (Fleet). As of 2017, it is also known as Chief of Fleet Support, Chief of Materiel (Ships) then as of 2020, Director General Ships.

The Admiralty was a department of the Government of the United Kingdom responsible for the command of the Royal Navy until 1964, historically under its titular head, the Lord High Admiral – one of the Great Officers of State. For much of its history, from the early 18th century until its abolition, the role of the Lord High Admiral was almost invariably put "in commission" and exercised by the Lords Commissioner of the Admiralty, who sat on the governing Board of Admiralty, rather than by a single person. The Admiralty was replaced by the Admiralty Board in 1964, as part of the reforms that created the Ministry of Defence and its Navy Department.