Nikephoros Gregoras, Latinized as Nicephorus Gregoras (Greek: Νικηφόρος Γρηγορᾶς; c. 1295-1360), Byzantine astronomer, historian, man of learning and religious controversialist, was born at Heraclea Pontica.
At an early age he settled at Constantinople, where his reputation for learning brought him under the notice of Andronicus II Palaeologus, by whom he was appointed chartophylax (keeper of the archives). In 1326 Gregoras proposed (in a treatise which remains in existence) certain reforms in the calendar, which the emperor refused to carry out for fear of disturbances; nearly two hundred years later they were introduced by Gregory XIII on almost the same lines.
When Andronicus was dethroned (1328) by his grandson Andronicus III Palaeologus, Gregoras shared his downfall and retired into private life. Attacked by Barlaam, the famous monk of Calabria, he was with difficulty persuaded to come forward and meet him in a war of words, in which Barlaam was worsted. This greatly enhanced his reputation and brought him a large number of pupils.
Gregoras remained loyal to the elder Andronicus to the last, but after his death he succeeded in gaining the favour of his grandson, by whom he was appointed to conduct the unsuccessful negotiations (for a union of the Greek and Latin churches) with the ambassadors of Pope John XXII (1333). Gregoras subsequently took an important part in the Hesychast controversy, in which he violently opposed Gregorius Palamas, the chief supporter of the doctrine. After the doctrines of Palamas had been recognized at the synod of 1351, Gregoras, who refused to acquiesce, was practically imprisoned in a monastery for two years. Nothing is known of the end of his life.
His chief work is his Roman History, in 37 books, of the years 1204 to 1359. It thus partly supplements and partly continues the work of George Pachymeres. Gregoras shows considerable industry, but his style is pompous and affected. Far too much space is devoted to religious matters and dogmatic quarrels. This work and that of John Cantacuzene supplement and correct each other, and should be read together.
The other writings of Gregoras, which (with a few exceptions) still remain unpublished, attest his great versatility. Amongst them may be mentioned a history of the dispute with Palamas; biographies of his uncle and early instructor John, metropolitan of Heraclea, and of the martyr Codratus of Antioch; funeral orations for Theodore Metochites, and the two emperors Andronicus; commentaries on the wanderings of Odysseus and on Synesius's treatise on dreams; tracts ‘on orthography and on words of doubtful meaning; a philosophical dialogue called Phlorentius or Concerning Wisdom; astronomical treatises on the date of Easter, on the preparation of the astrolabe and on the predictive calculation of solar eclipses; and an extensive correspondence.
Editions: in Bonn Corpus senitorum hist. Byz, by L. Schopen and I. Bekker, with life and list of works by J. Boivin (1829–1855); J. P. Migne, Patrologia Graeca, cxlviii., cxlix.; see also Karl Krumbacher, Geschichte der byzantinischen Litteratur (1897).