The Iron Duke-class was a group of four dreadnought battleships built for the Royal Navy before the First World War. The class comprised four ships: Iron Duke, Marlborough, Benbow, Emperor of India. Launched from October 1912 to November 1913, this was the third class of Royal Navy super-dreadnoughts. The ships were essentially repeats of the King George V-class battleships; they retained the same ten BL 13.5"/45-caliber Mk.V naval guns in five twin gun turrets on the centreline. However, the Iron Dukes had improved armour and a more powerful secondary armament of 6-inch weapons instead of the 4-inch mounted on the earlier ships.
The six ships were the most advanced battleships in the Royal Navy at the outbreak of the First World War, though they were soon surpassed by the five ships of the Queen Elizabeth-class. They all saw extensive service during the war with the Grand Fleet, where Iron Duke acted as the flagship for the fleet commander, Admiral John Jellicoe. Three of the ships, Iron Duke, Benbow, and Marlborough, were present at the Battle of Jutland; the Emperor of India missed the battle by being in dock for periodic refit. The six Iron Duke-class battleships saw limited active duty following the end of the war; they were all demilitarised under the terms of the Washington Naval Treaty signed in 1922. Iron Duke was turned into a museum ship in 1926. Benbow was scrapped in 1931 and Marlborough followed in 1932. Emperor of India was sunk as a gunnery target in 1931.
- HMS Iron Duke - turned into museum ship, 1926
- HMS Marlborough
- HMS Benbow
- HMS Emperor of India