My research concerns the origins and early use of a large body of forged laws concocted in the middle of the ninth century, known collecitvely as the Pseudo-Isidorian decretals. These laws were drafted by a group of monastic forgers at the Abbey of Corbie; their creators had wide-ranging goals, but they aimed above all to defend diocesan bishops from the power of higher ecclesiastical and secular authorities. Together, the interrelated texts associated with Pseudo-Isidore approach the length of the Bible, and they went undetected for centuries after their development, exercising a deep and enduring influence on the institutional and legal history of Christianity in the West. I hope to synthesize and build upon earlier philological and historical research to form a picture of precisely when and how these forged laws were first assembled, and how the arguments they contain were intended to interact with the broader political and religious world of Carolingian Europe.