The patriarchate of Constantinople is one of the most renowned and enduring ecclesiastical institutions of the Christian East. With a history dating from the fourth century until the present day, the patriarchate played a crucial role in the religious and ecclesiastical life of Orthodox communities and, even more so, in the political and cross-cultural landscape of a broad region that stretches from the Mediterranean lands to Muscovy via the Caucasus. As such, it has received a significant degree of attention from scholars, who have made available not only documents of paramount importance for its diplomatic history, but also detailed studies on various aspects of its ecclesiastical role in the region, as well as its relations with other Churches. Since, over the past years, research on the patriarchate had mainly emanated from Byzantinists affiliated to the Austrian Academy of Sciences and the University of Vienna, it is no suprise that this volume in Brill's Companions to the Byzantine World series was edited by a team of distinguished Viennese scholars. Christian Gastgeber, Ekaterini Mitsiou, Johannes Preiser-Kapeller and Vratislav Zervan have overseen the production of this first overview of the patriarchate of Constantinople through thirteen essays, in English, authored by eminent scholars. Throughout, the editors have sought to emphasise ‘continuities and changes in the organizational, dogmatic, and intellectual framework of the central ecclesiastical institution of the Byzantine Empire’ (back cover).

The book opens with a detailed chapter by Claudia Rapp on the elevation and development of the patriarchate in its wider Mediterranean context until 726, with a focus on its place within the Eastern Churches, its financial situation and administrative structure. This is followed by Frederick Lauritzen's analysis of the patriarchal synod during the Middle Byzantine period, which tackles issues regarding the relationship between the patriarch and the synod and the role of the synod as tribunal. Next, Tia Kolbaba's contribution explores contacts and debates between the patriarchate and the Latin Church until 1204 from an ecclesiastical, political and theological perspective. Johannes Preiser-Kapeller then considers the late Byzantine synod as a leading administrative ecclesiastical body and studies its attributions, membership and decision-making process. Discussion on the relationship between the Latin Church and the patriarchate resumes with Marie-Hélène Banchet's chapter which focuses on the union between the Eastern and Western Churches during the Palaiologan period. A significant addition to the companion is the contributions by Dimitris Apostolopoulos and Machi Païzi-Apostolopoulos: these explore the situation of the Ecumenical Patriarchate after the fall of Constantinople by addressing key aspects of change and continuity in the patriarchate's administrative structure under Ottoman rule.

While the tangled relationship between the patriarchate and the Eastern Greek Orthodox patriarchates of Alexandria, Antioch and Jerusalem are described in detail by Klaus-Peter Todt, the patriarchate's role in the development of the Balkan Churches (i.e. the Bulgarian Church, the archbishopric of Ohrid and the Serbian patriarchate) is elegantly analysed by Mihailo Popović. Further, Konstantinos Vetochnikov offers an overview of the influence of the Byzantine patriarchate on the ecclesiastical life of the newly-emerged Orthodox Churches in the Russian lands. The description of the intricate relationship between the emperor and the patriarch is provided by Ekaterini Mitsiou, who investigates the political attitudes and power structure of the two actors within the imperial framework. Vratislav Zervan turns to intellectual history and inspects the scholarly functions of the patriarchs, as well as the patriarchate's institutions of learning. The volume ends with Christian Gastgeber's contribution, which masterfully explores the patriarchate's diplomatic history by investigating codicological and paleographical aspects of official chancellery documents, especially those offered in the register of the patriarchate of Constantinople, preserved today in the Austrian National Library.

In the absence of an introduction, which might have elucidated the internal organisation of the volume, readers only become aware of editorial decisions as they work through the volume. The essays are organised thematically and discuss the patriarchate's history somewhat diachronically from its rise in the fourth century until its restoration under the Ottomans. Nevertheless, the reader's experience would have benefited more if some chapters, which clearly complement each other very well, had been arranged slightly differently. For example, the reader's understanding of the complete picture of the patriarchate's relations with the Latin Church would have been greater if Blanchet's chapter had immediately followed Kolbaba's piece, rather than following Preiser-Kapeller's detailed article on the patriarchal synod during Late Byzantium, which itself could have come after Lauritzen's chapter and thus offered to readers a connected outline of the Byzantine synod. Moreover, since the situation of the patriarchate under the Ottoman rule was presented in chapters v and vi by Apostolopoulos and Païzi-Apostolopoulos, their contributions could have served the diachronic perspective more if placed towards the end of the volume, and their slot could have been filled by the studies by Todt, Popović and Vetochnikov.

Although recent years have witnessed a growing interest in publications featuring a plethora of companions, handbooks, sourcebooks and encyclopedias on all sorts of topics (and of varying quality), this particular volume is none the less a significant contribution in its field. It responds to a longstanding need for an introduction to the patriarchate of Constantinople, and thus fills a historiographical gap in Byzantine studies. Moreover, it provides Byzantinists and all who desire to explore and understand the intricate history of this institution with high-quality overviews of various aspects of the patriarchate’s history, consistent bibliographical lists which follow each chapter, and a statement of the state of research which, moreover, indicates new avenues of research, which will enrich future understanding of this enduring institution.