HMS Defence was the lead ship of the Defence-class armoured frigates ordered by the Royal Navy in 1859.

Defence had short tours on the North Atlantic and Mediterranean Stations, relieving other ironclads, from 1869 to 1872 before she was refitted again from 1872 to 1874.

The Defence-class ironclads[Note 1] were designed as smaller and cheaper versions of the Warrior-class armoured frigates.

This meant that they could not fit the same powerful engines of the Warrior-class ships and were therefore 2 knots (3.7 km/h; 2.3 mph) slower and had far fewer guns.

The naval architect Sir Nathaniel Barnaby, a future Constructor of the Navy, considered that in terms of combat a Defence-class ship was worth one quarter of a Warrior.

The hull was subdivided by watertight transverse bulkheads into 92 compartments and had a double bottom underneath the engine and boiler rooms.

[3] The Defence-class ships had one 2-cylinder trunk steam engine made by John Penn and Sons driving a single propeller.

The ship carried 450 long tons (460 t) of coal,[6] enough to steam 1,670 nautical miles (3,090 km; 1,920 mi) at 10 knots (19 km/h; 12 mph).

Firing tests carried out in September 1861 against an armoured target, however, proved that the 110-pounder was inferior to the 68-pounder smoothbore gun in armour penetration and repeated incidents of breech explosions during the Battles for Shimonoseki and the Bombardment of Kagoshima in 1863–1864 caused the navy to begin to withdraw the gun from service shortly afterwards.

[12] The Defence-class ships had a wrought iron armour belt, 4.5 inches (114 mm) thick, that covered 140 feet (42.7 m) amidships.

The ship returned to the Channel Fleet in 1868, and in 1869 she was sent to the North America station to relieve HMS Royal Alfred.

She served with the Mediterranean Fleet from 1871 to 1872[8] under the command of Captain Nowell Salmon, who had earned the Victoria Cross during the Indian Mutiny in 1857.

On 20 July 1884 the ship collided with HMS Valiant in Lough Swilly, damaging her bow and flooding some compartments.