This chapter provides a brief overview of criminology of religion. The term "religious" has to do with organized religion, not only institutional doctrines, rituals, and activities but also an individual's perceptions and experiences associated with them. The chapter begins with a critical analysis of criminological theories of desistance, followed by a review of previous studies on religion and desistance. It discusses how the concept of spirituality as well as religion would contribute to the explanation of criminal desistance. While conceptual and measurement issues of desistance have not been fully resolved among criminologists, a consensus has been the conceptualization of desistance as a process rather than being confined to a discrete event. As theories of desistance were being introduced, researchers examined whether religion contributes to desistance among offenders, including those in prison during incarceration and after release. Finally, the chapter proposes a theory of existential identity transformation along with suggested measurement of existential identity for future research on religion and desistance.