Gregory Palamas (; Byzantine Greek: Γρηγόριος Παλαμᾶς, romanized: Grēgórios Palamâs, pronounced [ɣriˈɣo.ri.os pa.laˈmas]; c. 1296 – 14 November 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 Thessalonica, 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 Post Vatican II Catholic Church, he has also been called a saint; Pope John Paul II repeatedly called Gregory a great theological writer. 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 of Gregory Palamas in most branches of the Eastern Orthodoxy, while in some Eastern Catholic Churches, the issue is disputed.
