This chapter synthesizes perspectives on identity development in childhood, adolescence, and adulthood in terms of a broad conceptual model that identifies three strands of identity development across the human life course. The first strand of identity development involves the performance of traits and roles, eventuating in the establishment of a reputation as a social actor. The second strand begins with the consolidation of theory of mind in early childhood and the development of identity as a goal-directed, motivated agent. Beginning with the emergence of autobiographical reasoning in adolescence, identity development also follows the third strand of the autobiographical author who reconstructs the past and imagines the future in terms of an evolving and internalized life narrative. A person’s life story provides that sense of temporal sameness and continuity that Erikson imagined to be a defining feature of identity. A full understanding of identity requires a consideration of how all three strands – the self as actor, agent, and author – develop and interact over the human life course.