Proclus Diadochus (410-485) was a Byzantine philosopher and the last of the great Neoplatonists of antiquity. His philosophy indirectly influenced Christian thought, and he directly influenced many Renaissance thinkers.

Proclus was born in Constantinople (modern Istanbul) of Lycian parentage. He received his elementary education in Xanthus and then continued his studies in Alexandria. Among his teachers were the Sophist Leonas of Isauria and the Egyptian grammarian Orion as well as a number of Roman teachers, who taught him Latin. His basic study was rhetoric, since his intention originally was to enter the legal profession. However, on a trip to Constantinople with Leonas, Proclus appears to have been "converted" to philosophy, and on his return to Alexandria he studied Aristotle and mathematics. At the age of 19 he went to the Platonic Academy in Athens, where he studied under Plutarch of Athens, founder of the Athenian school of Neoplatonism, and Syrianus, Plutarch's immediate successor.

Syrianus greatly influenced Proclus's philosophical development, and he regarded Proclus both as his pupil and as his successor at the Academy. Under Syrianus's tutelage, Proclus read widely in Plato and Aristotle, and at 28 he had produced a number of sophisticated commentaries on different dialogues of Plato, including the monumental commentary on the Timaeus. When Syrianus died, the chair passed briefly to Domninus of Larissa, and it was then assumed by Proclus, who held it until his death.

According to a contemporary biographer, Proclus possessed great bodily strength and endurance and striking physical beauty. He was a practicing magician, a vegetarian, and a man of great personal asceticism. Apart from his professional teaching and writing, he must have at least occasionally spoken his mind on politics, since he left Athens at one time for a year, when political enemies were attempting to put him on trial.

In addition to his commentaries on Plato's dialogues and a commentary on Plotinus's Enneads, Proclus wrote important works on systematic philosophy and theology. They include the Elements of Theology and the Platonic Theology, as well as smaller treatises: Doubts about Providence, Providence and Fate, The Continuance of Evil, and Conduct. He also wrote commentaries on the Chaldean oracles, the first book of Euclid's Elements, and the poets Hesiod and (possibly) Homer, several astronomical treatises, a treatise on the elements of physics, and a large number of hymns to different gods.