Since A.-J. Festugiere’s pioneering study “Proclus et la religion traditionnelle” (1966), several important researches have been devoted to the philosophical piety in Late Antiquity in the last three decades. The present project follows this line of research and focuses on a less studied aspect, namely on the theories and the practices of prayer (euche) formulated in the philosophical traditions of Late Antiquity, mainly in Neo-Platonism. On the basis of case studies dedicated to essential texts regarding the philosophical and theological problem of prayer (Maximus of Tyr, Dissert. V; Porphyry, Epistula ad Anebonem, De philosophia ex oraculis haurienda; Iamblichus, De mysteriis; Sallustius, De deis et mundo; Proclus, in Timaeum, etc.), this project deals with some problems which either have never been raised before, or have been discussed in a general and superficial manner: the relation between prayer and knowledge, between prayer and providence, the relation between philosophical piety and the civic cult; the exegetical activity as a religious act, as a sui generis prayer. By its innovative character, the present project is likely to bring a significant contribution to the study of the philosophical appropriations of the traditional religious practices in Late Antiquity.