This reference work provides a comprehensive biographical record of every individual who has held the office of the papacy, including those contested as antipopes. The text, originally authored by J.N.D. Kelly and updated by Michael J. Walsh, utilizes historical records to document the lineage, social origins, and administrative actions of each pontiff. It serves as a structured academic resource for understanding the evolution of the papal office from its inception to the modern era.

Scholars and historians frequently cite this volume as a standard, reliable reference for ecclesiastical history. Readers note the clarity of the entries and the utility of the chronological organization for tracking the development of the papacy over two millennia.