Basilios (or Basilius) Bessarion (in Greek Βασίλειος Βησσαρίων) (2 January 1403 – 18 November 1472), a Roman Catholic Cardinal Bishop and the titular Latin Patriarch of Constantinople, was one of the illustrious Greek scholars who contributed to the great revival of letters in the 15th century. He has been mistakenly known also as Johannes Bessarion or Giovanni Bessarione due to an erroneous interpretation of Gregory III Mammas.
He was born in Trebizond, the Black Sea port in northeastern Anatolia that was the heart of Pontic Greek culture and civilization during the Byzantine and Ottoman periods. The year of his birth has been given as 1389, 1395 or 1403.
He was educated in Constantinople, and went in 1423 to the Peloponnese to hear Gemistus Pletho expound the philosophy of Plato. On becoming a tonsured monk, he adopted the name of an old Egyptian anchorite Bessarion, whose story he has related. In 1436 became abbot of a monastery in Constantinople and in 1437, he was made metropolitan of Nicaea by the Byzantine Emperor John VIII Palaeologus, whom he accompanied to Italy in order to bring about a reunion between the Orthodox and Catholic churches. They had been separated since the Schism of 1054, but the emperor hoped to use the possibility of re-uniting the churches to obtain help from Western Europe against the Turks. Bessarion participated in the Byzantine delegation to the Council of Ferrara-Florence as the most eminent representative of unionists, although originally belonged to the party of anti-unionists. On 6 July 1439 he was the one who read the declaration of the Greek Association of Churches in the cathedral of Florence, in the presence of Pope Eugene IV and the Emperor John VIII Palaeologus.