The Prince Consort class of battleship were four Royal Navy wooden-hulled broadside ironclads: HMS Royal Oak, HMS Prince Consort, HMS Ocean, and HMS Caledonia. They were originally laid down as Bulwark-class battleships, but were converted to ironclads. Royal Oak was Britain's fifth ironclad battleship completed. Prince Consort, Ocean, and Caledonia were built to a common design and are today known as the Prince Consort class, though contemporaries knew them as the Caledonia class. Royal Oak was their half-sister.