Prochoros Kydones (Greek: Πρόχορος Κυδώνης; c. 1330 – c. 1369), Latinized as Prochorus Cydones or Prochorus Cydonius was an Eastern Orthodox monk, theologian, and linguist. An advocate of Western Aristotelian thought, his translation of Latin Scholastic writings, brought him into conflict with Hesychasm, the leading school of Byzantine mystical theology, and its most vigorous defender, Gregory Palamas.
Born in the Byzantine city of Thessalonica, Prochoros entered the Great Lavra, a monastery on Mount Athos at a young age, and was eventually ordained a hieromonk. He was greatly influenced by Western Scholasticism. He collaborated with his brother Demetrios Kydones in translating Thomas Aquinas' monumental Summa Theologiae. Prochoros also made Greek translations of the works of Augustine of Hippo and the 6th-century philosopher Boethius.
Prochoros' own treatise, De essentia et operatione Dei (“On the Essence and Activity of God”), was a condemnation of the mystical theology of Hesychasm, propagated by Gregory Palamas. The Synod of Constantinople in 1368 condemned both of the brothers Kydones as heretics, and Prochoros was deposed from the priesthood. The chief source for Prochoros' life is a pair of polemical addresses by Demetrios, eulogizing his brother and denouncing Patriarch Philotheus Kokkinos, who had been responsible for their condemnation. He died at Mount Athos.