The Martyrs of Otranto, also known as Saints Antonio Primaldo and his Companions (Italian: I Santi Antonio Primaldo e compagni martiri), were 813 inhabitants of Otranto, Salento, Apulia, in southern Italy, who were killed on 14 August 1480 after the city had fallen to an Ottoman force under Gedik Ahmed Pasha. According to a traditional account, the killings took place after the citizens had refused to convert to Islam.

The Ottoman ambitions in Italy were ended. Had Otranto surrendered to the Turks, the history of Italy might have been very different. But the heroism of the people of Otranto was more than a strategically decisive stand. What made the sacrifice of Otranto so remarkable was the willingness to die for the faith rather than reject Christ.

The siege of Otranto, with the martyrdom of its inhabitants, was the last significant military attempt by a Muslim force to conquer southern Italy. The slaughter was remembered by historians of the Risorgimento like Girolamo Arnaldi and Alfonso Scirocco as a milestone in European history because the sacrifice had the consequence that the Italian Peninsula was never conquered by Muslim troops. The martyrs were presented as civic heroes representing the strength and fortitude of the Italian people.

On 28 July 1480, an Ottoman force, which was commanded by Gedik Ahmed Pasha, consisting of 90 galleys, 40 galiots and other ships and carrying a total of around 150 crew and 18,000 troops, landed beneath the walls of Otranto. The city strongly resisted the Ottoman assaults, but the garrison was unable to withstand the bombardment for long. The garrison and all of the townsfolk thus abandoned the main part of the city on 29 July and retreated into the citadel, and the Ottomans began bombarding the neighboring houses.

According to accounts of the story chronicled by Giovanni Laggetto and Saverio de Marco, the Ottomans promised clemency if the city capitulated but were informed that it would never surrender. A second Ottoman messenger was sent to repeat the offer but "was slain with arrows and an Otranto guardsman flung the keys of the city into the sea". The Ottoman artillery then resumed its bombardment.

A messenger was dispatched to beseech King Ferdinand I of Naples for assistance, but most of the Aragonese militias were already committed in Tuscany. "Nearly seven eighths (350) of Otranto's militia slipped over the city walls and fled". The remaining fifty soldiers fought alongside the citizenry and dumped boiling oil and water onto the Ottomans who were trying to scale the ramparts between the cannonades.

The citadel fell after a 15-day siege on August 12. After the walls had been breached, the Ottomans began fighting their way through the town. Upon reaching the cathedral, "they found Archbishop Stefano Agricolo, fully vested and crucifix in hand", who was awaiting them with Count Francesco Largo. "The archbishop was beheaded before the altar, his companions were sawn in half, and their accompanying priests were all murdered". After desecrating the cathedral, the Ottomans gathered the women and older children to be sold into Albanian slavery. Men over 15, small children and infants were slain.

According to some historical accounts, a total of 12,000 were killed and 5,000 enslaved, including victims from the territories of the Salentine Peninsula around the city.