Gregory Palamas, Greek archbishop and saint (b. 1296)
Gregory Palamas (Greek: Γρηγόριος Παλαμᾶς; c. 1296 – 1357 or 1359) was a Byzantine Greek theologian and Eastern Orthodox cleric of the late Byzantine period. A monk of Mount Athos (modern Greece) and later archbishop of Thessaloniki, he is famous for his defense of hesychast spirituality, the uncreated character of the light of the Transfiguration, and the distinction between God's essence and energies (i.e., the divine will, divine grace, etc.). His teaching unfolded over the course of three major controversies, (1) with the Italo-Greek Barlaam between 1336 and 1341, (2) with the monk Gregory Akindynos between 1341 and 1347, and (3) with the philosopher Gregoras, from 1348 to 1355. His theological contributions are sometimes referred to as Palamism, and his followers as Palamites.

Gregory has been venerated as a saint in the Eastern Orthodox Church since 1368. Within the Catholic Church, he has also been called a saint, and repeatedly cited as a great theological writer, by Pope John Paul II. Since 1971, the Melkite Greek Catholic Church has venerated Gregory as a saint. Some of his writings are collected in the Philokalia, and since the Ottoman period, the second Sunday of Great Lent is dedicated to the memory Gregory Palamas in the Orthodox Church and Ukrainian Greek Catholic Church. The Byzantine Synodikon of Orthodoxy also celebrates his memory and theology while condemning his opponents, including some anti-Palamites who flourished after Gregory's death.