By Terry Odenigbo
They were beheaded in the southern Italian town of Otranto after refusing to convert to Islam.
Their names are unknown, apart from one man, Antonio Primaldo.
Within two months of taking office, Pope Francis has proclaimed more saints than any of his predecessors.
Among those canonised on Sunday were two Latin American nuns – Laura Montoya from Colombia and Maria Guadalupe Garcia Zavala from Mexico – who both died in the 20th Century.
Colombia’s first saint, Mother Laura Montoya dedicated her life to helping indigenous people while the woman named by Pope Francis as Mother “Lupita” sheltered Catholics during a government crackdown against the faith in the 1920s.
The Italian “Martyrs of Otranto” were executed after 20,000 Turkish soldiers invaded their town in south-eastern Italy.
There was no hint of any anti-Islamic sentiment in the homily that Pope Francis delivered before tens of thousands of worshippers gathered in St Peter’s Square, the BBC’s David Willey in Rome reports.
While it was Francis’s predecessor, Pope Benedict, who gave the go ahead for their canonisations, the new pope is continuing the process of honouring a new generation of modern as well as historic martyrs, our correspondent says.
Later this month an Italian priest, Fr Giuseppe Puglisi, who was murdered by the Sicilian mafia 20 years ago will be beatified – the last step before being declared a saint.