Affondatore was an armoured ram of the Regia Marina (Italian Royal Navy), built in the 1860s by Harrison, Millwall, London.

Affondatore, which translates as "Sinker", was initially designed to rely on her ram as her only weapon, but during construction she was also equipped with two 300-pounder guns.

On 11 October 1862, early in the Austro-Italian ironclad arms race, the Italian Navy placed an order with the British shipyard Mare of Millwall, London, for an armoured steam ram, to a design by the Italian naval officer Simone Antonio Saint-Bon, but financial problems resulted in the order being transferred to the shipyard Harrison, also of Millwall.

Sufficient coal was carried to give a range of 1,647 nautical miles (3,050 km; 1,895 mi) at 10 knots (19 km/h; 12 mph).

Affondatore left Cherbourg on 20 June, the day Italy declared war, sailing to join the main Italian fleet which was operating in the Adriatic Sea.

Persano claimed he was simply waiting for Affondatore to arrive, but his inaction weakened morale in the fleet, with many of his subordinates openly accusing him of cowardice.

In response, the Austrian Navy sent the fleet under Rear Admiral Wilhelm von Tegetthoff to attack the Italian ships.

After arriving off Lissa on the 18th,[8] Persano spent two days unsuccessfully trying to suppress the Austrian gun batteries on the island so he could land the soldiers.

[9] Affondatore joined the fleet after it had arrived off Lissa on 19 July,[10] but her crew were not fully worked up and had struggled to handle the ship while sailing to Italy and the Adriatic.

[11][12] Persano decided to make a third attempt to force a landing on the 20th, but before the Italians could begin the attack, the dispatch boat Esploratore arrived, bringing news of Tegetthoff's approach.

Shortly before the action began, Persano decided to leave his flagship, Re d'Italia, and transfer to Affondatore, though none of his subordinates on the other ships were aware of the change.

Tegetthoff took his fleet through the gap between Vacca's and Persano's ships, though he failed to ram any Italian vessels on the first pass.

Persano initially kept his ship out of the action, until after Re d'Italia had been rammed and sunk by the Austrian flagship, Erzherzog Ferdinand Max.

[16] According to naval historians Greene and Massignani, however, Affondatore merely took on too much water due to her low freeboard; the damage sustained at Lissa had nothing to do with her sinking.

[20] During the annual fleet maneuvers held in 1885, Affondatore served in the 2nd Division of the "Western Squadron"; she was joined by the ironclad Roma and five torpedo boats.

During the maneuvers, which lasted from 6 August to 5 September, the ships of the Active Squadron simulated a French attack on the Italian fleet.