This article aims to reopen and advance the discussion of the geographic location of Pseudo-Dionysius the Areopagite, the author of the Corpus Dionysiacum. While various locales, for example, Antioch and Alexandria, have been proposed, none of the hypotheses about Dionysius's identity and location has to date gained the universal acceptance among scholars. This study shows that the baptismal rites described in the second chapter of Pseudo-Dionysius's Ecclesiastical Hierarchy and in the fifth century Ordo of Constantinople, recorded in the Euchologion Barberini gr. 336, have several unique features in common, such as the threefold renunciation of Satan, balanced by the threefold profession of faith, and the blessing of the baptismal water with the consecrated oil. These features are not attested by any other source contemporary or earlier than the Ecclesiastical Hierarchy and the material of the Ordo. Based on these unique similarities the author advances a new hypothesis that Pseudo-Dionysius describes a Constantinopolitan rite and very likely lived in Constantinople at some point in his career. Six objections to this hypothesis are considered and answered in the second part of the paper.