HMS Caledonia was a broadside ironclad of the Prince Consort class. Originally laid down as a two-decker steam ship of the line of the Bulwark class, Caledonia was converted on the building stocks into an armoured frigate.

HMS Caledonia was not completed until July 1865 due to a delay in the delivery of her main armament. Once this was installed, she was commissioned as Second-in-Command of the Mediterranean Fleet, becoming the first ever armoured flagship of the Royal Navy.

She was temporarily withdrawn from service in 1866 for reconstruction which involved the addition of a poop deck. Following this, she was flagship of the Channel Fleet until 1867, when she was paid off for re-armament.

HMS Caledonia was flagship of the Mediterranean Fleet until 1869 (relieving HMS Victoria, the last three-deck Royal Navy flagship) until 1872.^{[citation needed]} In July 1871, she ran aground off Santorini, Greece. She was later refloated and taken in to Malta for repairs. She was a guardship in the Firth of Forth from 1872 until 1875.^{[citation needed][dubious – discuss]} On 15 June 1873, Caledonia was in collision with the British ship Hogton Tower off St. Alban's Head, Dorset. Hogton Tower was severely damaged at the bows; Caledonia towed her in to Spithead, Hampshire. Caledonia had been serving as a Coastguard vessel at Birkenhead, Cheshire and was sailing to Portsmouth, Hampshire for a forthcoming inspection of the fleet by the Shah of Persia. She was paid off at Plymouth, and was laid up there until she was sold on 30 September 1886.^{[citation needed]}