What is an activist identity? Prior answers have focused almost exclusively on collective identity, without (a) considering the possibility of role-based identities or (b) grounding collective identities in broader social-psychological theories. The present study investigates activist identity through the lens of role-based and category-based identities and reports two major findings. First, there is a distinct role-based activist identity, one that involves internalizing role responsibilities and the expectations of friends and family. Second, collective identity represents a relationship between a social identity and an injustice frame; it either involves incorporating an injustice frame into a preexisting social identity or using the injustice frame to create a new in-group. The present findings help to illuminate the processes underlying collective identity, indicate that a great deal of role-based activist identity is mistaken for collective identity, and suggest new directions for the study of micro-mobilization and organizational forms and tactics in social movements.