City Readers Digital Historic Collections at the New York Society Library

Pseudo-Dionysius the Areopagite (Greek: Διονύσιος ὁ Ἀρεοπαγίτης), also known as Pseudo-Denys, was a Christian theologian and philosopher of the late 5th to early 6th century, who wrote a set of works known as the Corpus Areopagiticum or Corpus Dionysiacum.

The author pseudonymously identifies himself in the corpus as "Dionysios", portraying himself as the figure of Dionysius the Areopagite, the Athenian convert of Paul the Apostle mentioned in Acts 17:34. This false attribution to the earliest decades of Christianity resulted in the work being given great authority in subsequent theological writing in both East and West.

The Dionysian writings and their mystical teaching were universally accepted throughout the East, amongst both Chalcedonians and non-Chalcedonians, and also had a strong impact in later medieval western mysticism, most notably Meister Eckhart. Its influence decreased in the West with the fifteenth-century demonstration of its later dating, but in recent decades, interest has increased again in the Corpus Areopagiticum.