This study examines the impact of the eleventh-century ecclesiastical reform movement on ideologies and representations of female secular authority. The well-known reform movement redrew the boundaries between secular and ecclesiastical spheres across Europe and initiated an intellectual debate over conceptions of lay and religious rulership. Traditionally, scholars have seen the reform program as an oppressive force which sought with varying degrees of success to limit women’s participation in ecclesiastical affairs and to marginalize their presence in broader society. However, scholars have underestimated the significant presence of lay noblewomen in reform activities. This study locates women as key participants in the reform program, a surprising discovery given the strong associations made by many clerical supporters of reform between women and pollution, above all due to their sexuality. The dissertation takes a wide geographical focus, examining the impacts of the reform movement on female lordship across Latin Christendom in order to explore both similarities and differences in experience rather than search for a single model of female lordship. By focusing on textual representations of female agency and authority in contemporary narrative histories, letters, and hagiographical texts, the pages below demonstrate that the reform movement witnessed a period of creativity in the construction and representation of gendered secular authority, particularly in relation to the performance of power by laywomen. This study contributes to the growing scholarship focusing on the role of gender and women in religious and cultural history. Its main goal is to create a synthesis between studies of medieval lordship, church reform, and gender and women’s history.