Italian ironclad Regina Maria Pia

Map showing the disposition of the fleets on 20 July

On 16 July, Persano took the Italian fleet out of Ancona, bound for Lissa, where they arrived on the 18th. With them, they brought troop transports carrying 3,000 soldiers; the Italian warships began bombarding the Austrian forts on the island, with the intention of landing the soldiers once the fortresses had been silenced. In response, the Austrian Navy sent the fleet under Tegetthoff to attack the Italian ships.[5] Regina Maria Pia was at that time in the 3rd Division, commanded by Captain Augusto Riboty, along with the ironclads Terribile, Formidabile, and Re di Portogallo, and the coastal defense ship Varese.[6] After spending the 18th unsuccessfully bombarding the Austrian fortresses, the Italians withdrew late in the day, preparing to launch another attack the following morning. Persano sent most of his ships to bombard the town of Vis, but he was unable to effect the landing.[7]

The next morning, Persano ordered another attack; four ironclads would force the harbor defenses at Vis while Regina Maria Pia and the rest of the fleet would attempt to suppress the outer fortifications. This second attack also proved to be a failure, but Persano decided to make a third attempt the next day. Regina Maria Pia and the bulk of the fleet would again try to disable the outer forts in preparation for the landing.[8] Before the Italians could begin the attack, the dispatch boat Esploratore arrived, bringing news of Tegetthoff's approach. Persano's fleet was in disarray; the three ships of Admiral Giovanni Vacca's 1st Division were three miles to the northeast from Persano's main force, and three other ironclads were further away to the west.[9] Persano immediately ordered his ships to form up with Vacca's, first in line abreast formation, and then in line ahead formation. Regina Maria Pia initially was the last ship in the line, though Varese later joined up behind her.[10]

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. They were thus left to fight as individuals without direction. More dangerously, by stopping Re d'Italia, he allowed a significant gap to open up between Vacca's three ships and the rest of the fleet.[11] Tegetthoff took his fleet through the gap between Vacca's and Persano's ships, in an attempt to split the Italian line and initiate a melee. He failed to ram any Italian vessels on the first pass, so he turned back toward Persano's ships, and took Re d'Italia, San Martino, and Palestro under heavy fire. The Austrians quickly inflicted serious damage on Re d'Italia and Palestro. While Tegetthoff's ironclads were attacking Persano's division, Riboty's division, including Regina Maria Pia, engaged Anton von Petz's division of unarmored steam frigates. In the melee, Regina Maria Pia collided with San Martino, damaging the latter's ram bow.[12]

After Palestro withdrew, the Austrian ironclads turned their attention to the ships of Riboty's division. By this time, Re d'Italia had been rammed and sunk, and Palestro was burning furiously. Persano broke off the engagement to consolidate his forces, but his ships, low on coal and ammunition, and with badly demoralized crews, could not be rallied by Persano's half-hearted attempt to launch an attack. The Italian fleet began to withdraw, followed by the Austrians; as night began to fall, the opposing fleets disengaged completely, heading for Ancona and Pola, respectively.[13] Regina Maria Pia had had one iron plate destroyed, and another had a steel shot lodged in it. She had been badly burned, and the flames had nearly reached her powder magazine.[14] In return, she had damaged the Austrian ship of the line SMS Kaiser and the ironclad Prinz Eugen.[15] After the battle, Vacca replaced Persano; he was ordered to attack the main Austrian naval base at Pola, but the war ended before the operation could be carried out.[16]

Regina Maria Pia (right background) at the launch for the ironclad Italia in 1880. The other ships present are the Italian Principe Amedeo (behind Regina Maria Pia) and the British HMS Monarch and Thunderer (center background)

For the rest of her long career, Regina Maria Pia served in a variety of roles, both in the main fleet and in Italy's colonial empire.[17] In the immediate aftermath of the war, the Italian naval budget was drastically reduced; so significant were the cuts that the fleet had great difficulty in mobilizing its ironclad squadron to attack the port of Civitavecchia in September 1870, as part of the wars of Italian unification. Instead, the ships were laid up and the sailors conscripted to man them were sent home.[18] Some time after 1866, the ship was rebuilt as a central battery ship, with most of her guns located in a central, armored casemate. Two other guns were placed in the bow as chase guns, with a third mounted as a stern chaser. At this time, her armament was also revised, to two 220 mm (8.7 in) guns in the bow and nine 8 in guns, four on each broadside and the last in the stern.[1]

She was part of the international fleet that assembled at Tessaloniki during the Salonika Incident in May 1876 in response to the murder of the French and German consuls in the city.[19]

Regina Maria Pia took part in the launching ceremony for the ironclad Italia on 29 September 1880; also present were the Italian ironclad Principe Amedeo and King Umberto I aboard his yacht, and the British ironclads HMS Monarch (Captain George Tryon) and Thunderer of the Mediterranean Fleet.[20] Between 1888 and 1890, the ship had her barque rig replaced with military masts. By this time, she had been rearmed with eight 6 in (150 mm) guns in the casemate and several smaller guns for close-range defense against torpedo boats. These included five 4.7 in (120 mm) guns, four 57 mm (2.2 in) guns, and eight 37 mm (1.5 in) Hotchkiss revolver cannon. She also received three torpedo tubes.[1] The ship was stricken from the naval register in 1904 and subsequently broken up for scrap.[1]