Demetrius Cydonius, a theologian of the Greek Church, lived in the second half of the 14th century. He was born at Thessalonica or Bvzantium, and probably received his surname from the circumstance that he lived at Cydone in Crete. The emperor John Cantacuzenus, who was greatly attached to him, raised him to the highest posts of honor in the state. When this prince thought of embracing monastic life, Demetrius determined to leave the world also, and both entered the same convent in 1355. Subsequently he went to Italy to study the theology of the Latin Church, and while there became a friend of Thomas Aquinas and other prominent Latin theologians. The year of his death is not known; the latest incident in his life is a letter addressed in 1384 to the emperor Manuel Palaeologus, on the occasion of the latter ascending the throne. He is the author of a large number of works, and the translator of many Latin works into Greek. Most of his works have never been printed. His work, Περὶ τοῦ καταφρονεῖν τὸν θανατόν (de contemnenda morte, on contemning death), was published by R. Seiler (Basel, 1553), and by Kuinoel (Leipzic, 1786). A selection of his letters was published by Matthaei (Moscow 1776, and Dresden, 1789). For a list of his writings and their various editions, see Hoffmann, Bibliographisches Lexikon, 1:499; Fabricius, Bibliotheca Graeca, 1:498; see also Hoefer, Biographie Generale, 13:553.