The Ajax class of ironclad battleships consisted of two ships, HMS Ajax and HMS Agamemnon, serving in the Victorian era Royal Navy.

These two ships were built to the same concept as Inflexible - a heavily armoured citadel carrying four heavy guns mounted 'en echelon' in turrets to achieve all-round fire - but were required to be of lighter draught, and to displace 3,000 tons less.

Also, unlike the Inflexible, these ships were dependent upon the integrity of their unarmoured ends to maintain buoyancy; should the ends have been damaged enough to become waterlogged, the ships would have sunk.

This class were the last ships in the Royal Navy to be armed with muzzle-loading rifles, and the first to carry any form of secondary armament.

They were designed from the start not to carry any form of sailing rig.