John Laskaris Kalopheros (1325/30–1392) was a wealthy Byzantine aristocrat who converted to Catholicism and served as an advisor and diplomat to the Kingdom of Cyprus, the Papacy and the Republic of Venice.
He played a prominent role in negotiations to end to the East–West schism of the churches and launch a general crusade against the Ottoman Turks.
[5] When he secretly married Maria Kantakouzene, a daughter of Matthew Kantakouzenos, John V forced him into exile in 1362 or 1363.
[1][6] The reasons for the emperor's opposition to this marriage appear to be the threat that a man of Kalopheros' wealth and imperial pedigree posed when allied to a powerful family with a history of opposing the Palaiologoi.
[8] In exile, Kalapheros visited the court of Pope Urban V, who, on 18 April 1365, sent reference letters on his behalf to John V, King Peter I of Cyprus, the doges Lorenzo Celsi of Venice and Gabriele Adorno of Genoa and the Grand Master of the Knights Hospitaller.
[6] With a knight of Thessaloniki named Demetrios Angelos, a fellow convert and companion in exile, he took part in the Alexandrian Crusade in 1365.
[8] He took part in three campaigns in 1367: Peter's raid on Tripoli, Prince John of Lusignan's relief of besieged Corycus and the suppression of a rebellion at Adalia.
[1] He was in Cyprus in February 1373, when Queen Eleanor entrusted him with a message for her father, Peter of Ribagorza, then resident at Avignon.
[15] On 22 March, Pope Gregory XI sent him on a diplomatic mission to the Kingdom of Naples in an effort to coordinate a naval league against the Ottoman Turks.
[23] He left legacies for Jeannot de Soissons, the son of his stepson by his first wife, and to a daughter of his stepdaughter Alise by the same.