Within the social sciences and humanities, research into the formation and functioning of identity has gained much attention over the last few decades. However, each field has operated in relative isolation of the other. This dissertation draws together many different disciplines in order to better understand religious identity. Psychological research in identity has begun to question the notion of measuring a global identity for each person, and instead, to consider modular domains of identity functioning. First, the dissertation offers a theoretical background for religious identity. By thoroughly investigating the conceptual development of identity in Erik Erikson’s work, the project shows numerous insights into and problems with the current measurement paradigm of identity. It then looks at current research into autobiographical memory through cognitive science and considers several aspects of evolutionary psychology and identity. This section argues that religious identity is a core concept for the psychological study of religion, even though the field has largely overlooked this factor. Secondly, the project develops a conceptual foundation for an empirical measure of religious identity by first reviewing the current research in the interaction between religion and identity, and then by carefully laying out a foundation for religious identity salience and a reinterpretation of Marcia’s four identity statuses specific to religious identity functioning. Finally, the project offers a empirical project as a preliminary religious identity measurement. The measure is given to 650 participants and the data in described in detail. The dissertation shows that religious identity often implicitly functions in individuals in a subconscious fashion. Social approval bias and “deity approval bias” are suggested as explanations for explicit increases in reported religious identity salience. Finally, the data supports the conceptual validity of four religious identity statuses operating among the participants. Various results show that age and religious backgrounds are very important factors in religious identity formation.