The formation of communal identity has long been a topic of interest to scholars in a variety of disciplines. My dissertation investigates this issue from a new perspective through my examination of the construction of identity at three musical and ecclesiastical centers in medieval Aquitaine: the cathedrals of Saint-Étienne in Toulouse, Saint-Just-et-Saint-Pasteur in Narbonne, and Saint-Trophime in Arles. Using these case studies, I argue that the music, texts, and ritual actions of the liturgy were a critical element in forming communal identity in the Middle Ages. The impact of liturgies for the saints was particularly strong on the construction of identity because clerics often created their own, local rites in order to obtain the protection of these holy men and women against perceived threats, such as disputes with secular rulers or the perceived incursion of heresy. My project focuses on liturgies for the patron saint and the founder-bishop at Saint-Étienne, Saint-Just, and Saint-Trophime because the choice of a patron and the transmission of foundation legends were also a fundamental expression of the identity of a community, revealing how the clerics sought to position themselves in relation to their political neighbors and the larger Christian world. Sanctoral liturgies were created for use in a particular space, so in addition to analyzing liturgical music and texts my study examines the architecture and sculpture of the aforementioned sites. I focus on what the building programs reveal about the performance of liturgy at each locale and how these choices reinforced or sought to change the historical identity of the community. Although my work focuses on clerical communities in medieval Aquitaine, the implications of my interdisciplinary approach are much broader, providing a means toward a deeper understanding of the construction of identity in religious institutions throughout Latin Christendom in the Middle Ages.