Constantine Meliteniotes (Greek: Κωνσταντῖνος Μελιτηνιώτης, fl. 1240s – 2 April 1307) was a Greek ecclesiastical writer in the Byzantine Empire and a prominent supporter of the Union of Lyons between the Greek Orthodox Church and the Roman Catholic Church. He is best known as one of the two archdeacons of Patriarch John XI Bekkos who, together with him, were imprisoned and exiled in the years following the breakdown of the union; he remained under house arrest until his death.
Constantine Meliteniotes' surname implies that he had ancestral roots in the city of Melitene in southeast Anatolia. No precise information exists as to the place or date of his birth, but he speaks of himself as a native Byzantine, so one may assume that he was born either in Constantinople or in the Empire of Nicaea on the Asian side of the Bosporus. One recent study would date Meliteniotes' birth to between the years 1240 and 1250; another study suggests that he had, as a teacher, George Akropolites. Constantine Meliteniotes came from a fairly prominent Byzantine family; a number of men bearing his surname are known from late Byzantium, including the fourteenth-century writer Theodore Meliteniotes who, like Constantine, served as an archdeacon. Nevertheless, Constantine had no children; apparently he never married.
In June 1270, Constantine Meliteniotes was sent by Byzantine emperor Michael VIII Palaiologos (r. 1259–1282) on an embassy to King Louis IX of France, together with the then-chartophylax John Bekkos. The purpose of the embassy was to induce Louis to persuade his brother, Charles of Anjou, king of Sicily, to call off a planned assault upon Constantinople, which Michael VIII had recently recaptured from the Latins (1261). Louis was at that time outside the walls of Tunis, fighting a crusade against the Moslems; after a dangerous voyage, the two ambassadors reached Carthage on 3 August, and delivered to Louis gifts and a letter from the Byzantine emperor; when, finally, on 24 August 1270, they were granted an audience with the French king, Louis promised to do what he could to create better relations between Michael and his brother, but he in fact could do nothing, because he died the next day of dysentery; the Greek ambassadors had to sail home empty-handed.