HMS Iron Duke was a dreadnought battleship of the Royal Navy, the lead ship of her class, named in honour of Arthur Wellesley, 1st Duke of Wellington. She was built by Portsmouth Dockyard, and her keel laid in January 1912. Launched ten months later, she was commissioned into the Home Fleet in March 1914 as the fleet flagship. She was armed with a main battery of ten 13.5-inch (343 mm) guns and was capable of a top speed of 21.25 knots.

The Iron Duke class was a group of four dreadnought battleships built for the British Royal Navy before the First World War. The class comprised four ships: Iron Duke, Marlborough, Benbow, and 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 13.5 inch (34.3 cm) 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.