The Deputy Chief of the Naval Staff (DCNS) is a senior appointment in the Royal Navy currently held by the Second Sea Lord.^[1] The incumbent is usually a three-star rank and had a NATO ranking code of OF-8, but the position has previously been held by an acting two-star ranked officer and a four-star ranked officer.

The position was originally established in 1917 on the Board of Admiralty. It essentially replaced the position of Chief of the Admiralty War Staff.^[2]

The first incumbent was Vice Admiral Henry Oliver, the Chief of the Admiralty War Staff, who was appointed Deputy Chief of Naval Staff on 31 May 1917.^[3] The duties of the Deputy Chief of the Naval Staff, were shared with the First Sea Lord and Chief of the Naval Staff and with the Assistant Chief of the Naval Staff.^[2]

In September 1917 the new post of Deputy First Sea Lord was created to meet the demand of wartime operational requirements. The Deputy Chief of the Naval Staff then reported to the Deputy First Sea Lord until 1919 when that post was abolished. The Deputy Chief of the Naval Staff then resumed his previous role and reported to the First Sea Lord until 1941. Duties as of 1917 included:^[4][2][5]

1. Relieve the First Sea Lord of all the routine matters dealt with by sections under his immediate direction
2. Fleet Movements
3. All operations in the North Sea, the White Sea, the Baltic, and the Dover Area, except British coastal measures for the protection of trade
4. Offensive measures in the Mediterranean and abroad generally
5. The protection of trade in the North Sea, except the coastal trade on the East Coast of Great Britain. North Sea trade includes the Dutch trade, trade between Scandinavian countries and Great Britain, and Baltic trade, but not convoy from Lerwick, Southward
6. All questions relating to foreign stations, except protection of trade against submarine and mine attack
7. Policy of blockade and all questions relating thereto and to contraband of war
8. Organisation, movements and protection of troop transports and other vessels against attack by surface vessels; Atlantic convoys other than troop convoys being under the Assistant Chief of the Naval Staff

This remained in place until 1939. Duties after 1939 included:^[5]

1. Operations of War: All large Questions of Naval Policy and Maritime Warfare
2. Fighting and Sea-going Efficiency of the Fleet and its Organisation
3. Distribution and Movements of all Ships in Commission and in Reserve
4. Superintendence of the Naval Staff and the Hydrographic Department
5. Administering Naval communications
6. Superintendence of the Assistant Chief of the Naval Staff
7. Superintendence of the Director of the Naval Intelligence Division

In 1941 the DCNS post was renamed Vice Chief of the Naval Staff; this continued until 1946. After the Second World War the title was changed back to DCNS, and continued until 1968.

In 2013 the office was brought back once more and the current Deputy Chief of the Naval Staff became both a member of the Admiralty Board and a member of the Navy Board of the Ministry of Defence.

Duties circa March 2014 included:^[6]

• Full command of all deployable Fleet units including the Royal Marines
• Responsible for providing ships, submarines, aircraft and Royal Marine units ready in all respects for any operations that the UK Government requires
• Responsible for the delivery of the Naval Service's current and future personnel, equipment and infrastructure

Incumbents include:^[7]

Note: Post is renamed 1941 to 1946 its responsibilities are taken over by the Vice Chief of the Naval Staff

Note: From 1957 to 1965 the post was held jointly by the Fifth Sea Lord

Note: Post was vacant from 1969 to 2012; it was re-established in 2013. From 2013 to 2015 it was held by the Fleet Commander and from 2016 it was held by the Second Sea Lord

• Assistant Chief of the Naval Staff
• Vice Chief of the Naval Staff
• First Sea Lord
• Second Sea Lord
• Third Sea Lord
• Fourth Sea Lord
• Fifth Sea Lord