This dissertation reconsiders the phenomenon of religious change in Italy during the fourth and fifth centuries by arguing for the role of the visual arts in the formation of Christian identities. Contributing to the recent material turn in the study of early Christianity, which emphasizes the centrality of matter and the body in early Christian thought and practice, this project asserts that bishops and their congregations often employed the visual arts to construct and disseminate particular models of Christian identity. In addition to evoking Paradise and the presence of the divine, early ecclesiastical buildings and artistic programs appealed to the senses to persuade individuals to adopt certain beliefs, values, and practices consistent with emerging institutional Christianity. I focus in particular on the social dimensions of this identity, showing how specific sites in Rome, Aquileia, and Ravenna were designed to complement liturgical themes of ecclesiastical unity under episcopal authority. Working between theological texts and visual materials, I contextualize these case studies and show how each site responded to a wide array of social, political, and religious identities, including a diversity of private or domestic Christian beliefs and practices. Amidst this late antique context, ecclesiastical buildings and artistic programs rendered palpable to the senses an alternative social identity that emphasized membership and participation within a church community with a shared past, present, and future.