Sir Eustace Henry William Tennyson d'Eyncourt, 1st Baronet, KCB, FRS (1 April 1868 – 1 February 1951 was a British naval architect and engineer. As Director of Naval Construction for the Royal Navy, 1912–1924, he was responsible for the design and construction of some of the most famous British warships. On 20 February 1915 Winston Churchill appointed him Chairman of the Landships Committee at the Admiralty, which was responsible for the design and production of the first military tanks to be used in warfare.
D'Eyncourt was either the principal designer of the vessels listed below, or had ultimate responsibility for them.
Battleships and Battlecruisers
• Brazilian battleship, later HMS Agincourt, Turkish battleship, later HMS Erin, Chilean battleships Almirante Latorre, later HMS Canada and Almirante Cochrane, later HMS Eagle (aircraft carrier), Revenge-class battleship, Renown-class battlecruiser, HMS Hood battlecruiser, Several very large capital ship designs, both battleships and battlecruisers, rendered inadmissible under the Washington Naval Treaty, HMS Nelson battleship
Cruisers
• GRC Katsonis , HMS Chester, Arethusa class (1913), C class (1912–17), Caroline class, Calliope class, HMS Champion, Cambrian class, Centaur class, Caledon class, Ceres class, Carlisle class, Hawkins-class large cruisers (1915), Danae-class cruisers, (1916–18), HMS Danae, HMS Dragon, HMS Diomede, HMS Enterprise (Emerald-class cruiser)) (1917–18), HMS Kent (County-class cruiser) (1923–24)
"Large light cruisers", later aircraft carriers
• HMS Courageous, HMS Furious
Destroyers
• R and S-class destroyers, V and W-class destroyers, Scott-class flotilla leaders
Submarines
• J class, K class
Other types
Monitors, Patrol boats, Minesweepers, Sloops, Gunboats for China Station, Merchant ship conversions into seaplane carrier
Tanks
D'Eyncourt was chairman of the Landships Committee, created by Winston Churchill, which oversaw the design and production of Britain's first military tanks during World War 1.