HMS Duncan was the lead ship of the Royal Navy pre-dreadnought battleships. Commissioned in 1903, she served with the Mediterranean Fleet until 1905, at which she was transferred to the Channel Fleet.
Damaged in a collision with HMS Albion in late 1905, she was damaged again when she ran aground off Lundy Island. After a further stint with the Mediterranean Fleet, in 1913 she was assigned to the 6th Battle Squadron and based at Portsmouth, where she served as a gunnery training ship.
Decommissioned March 1919.