This edited volume deploys digital ethnography in varied contexts to explore the cultural roles of mobile apps that focus on religious practice and communities, as well as those used for religious purposes (whether or not they were originally developed for that purpose). Combining analyses of local contexts with insights and methods from the global subfield of digital anthropology, the contributors here recognize the complex ways that in-app and on-ground worlds interact in a wide range of communities and traditions. While some of the case studies emphasize the cultural significance of use in local contexts and relationships to pre-existing knowledge networks and/or non-digital relationships of power, others explore the globalizing and democratizing influences of mobile apps as communication technologies. From Catholic confession apps to Jewish Kaddish assistance apps and Muslim food apps, readers will see how religious-themed mobile apps create complex sites for potential new forms of religious expression, worship, discussion, and practices.