This multi-author instrument of reference offers an exhaustive inventory of the surviving works attributed to the prolific early third-century exegete and homilist Origen of Alexandria. The volume opens with an examination of two fourth-century inventories of Origen’s writings: a partial list of nineteen works and some letters made by Eusebius of Caesarea in the sixth book of his Ecclesiastical history; and a much longer list of seventy-seven titles in Jerome’s Letter 33 to Paula. The rest of the book presents individual entries for dozens of authentic writings of Origen as well as the handful of spurious works attributed to him. The editors have organised this material into four thematic sections (Old Testament Exegesis; New Testament Exegesis; a Miscellany of his Treatises and Letters, including the Hexapla and textual fragments; and Works Misattributed to Origen) comprising a total of twelve specific subsections, each written by a different author. Each individual entry comprises the following features: a brief introduction to the text, including information about its survival in Greek and its translation into other languages; a bibliography of premodern editions from the early modern editio princeps to the nineteenth century; a bibliography of modern critical editions and translations; and a curated list of books and articles that treat the text in question. The value of this volume for future research is beyond doubt. Scholars of Origen’s writings and reception will benefit tremendously from the resources marshalled in this book. One of the stated aims of the editors is to draw the attention of scholars to those works of Origen that remain unedited, including Jerome’s Latin translations of Origen’s homilies on Jeremiah, most of which survive in the original Greek (p. 117); and the twelfth-century Latin homily on Mary Magdalene of Cistercian provenance falsely attributed to Origen, which can be found in more than 185 manuscripts made between the thirteenth and sixteenth centuries (p. 260). No book is perfect, however. Aside from some minor typographical slips, inconsistencies and idiomatic errors, there are two issues that detract slightly from the utility of this volume as an instrument of reference. First, there are two new systems of shorthand codes for individual texts at work in the volume, neither of which is employed efficiently or consistently. It would have been much more helpful to key each work solely to its number in the Clavis Patrum Graecorum, which is the universally recognised inventory for Greek patristics. Second, the associated website (clavisorigenis.com) has little utility in its current iteration, as it links to a database of online resources related to patristics more generally rather than to bibliographical materials on Origen specifically. Despite these issues, however, scholars with an interest in Origen of Alexandria and the reception history of his writings in medieval and early modern Europe will surely benefit from consulting the Clavis Origenis.