Pseudo-Dionysius the Areopagite, unknown 5th century A.D. author of a collection of books falsely ascribed to the Dionysius mentioned in Acts 17:34. He was commonly believed to be this Dionysius, and he himself wrote as if he were. Today scholars generally agree he is not. His real identity is unknown, but he is thought to have been a Syrian monk.
Works: Mystical Theology, The Divine Names, The Ecclestiastical Hierarchy, The Celestial Hierarchy, and 10 letters. For the complete text of Mystical Theology, see [1].
His works show strong Neo-Platonic influence, (especially Proclus), as well as influence from Saint Clement of Alexandria, the Cappadocian Fathers, Origen, and others.
The great monastery of Saint Denis just north of Paris claimed to have the relics - the mortal remains - of Dionysius (Dionysius = Denis = Dennis). However, there are at least three Dionysiuses involved:
Peter Abelard, the 12th century theologian and philosopher, after his unfortunate experience with Heloise, became a Benedictine monk at Saint Denis. Around 1120 he was convicted of teaching Sabellianism and expelled for a short time. Upon his return around 1121, he turned his attention to the story of their patron saint, and disentangled the three Dionysiuses. The monks were offended, and Abelard did not remain long at Saint-Denis.
It was around 1500 that Lorenzo Valla did much to establish that Dionysius of the 5th Century could not have been St Paul's convert.