This essay reviews theory and research on moral identity. The construct emerged roughly three decades ago in moral psychology as a possible motivational factor that could link moral judgments to moral actions. Moral identity is, generally speaking, the extent to which being a moral person is important to a person's identity. However, it has been conceptualized and measured in various ways. In this essay, conceptualizations of moral identity, as well as foundational empirical research on moral identity development and links between moral identity and behavior, are reviewed. Little is known about moral identity development, but moral identity has fairly consistently been found predictive of moral action using a variety of research methods. In addition, cutting‐edge research on new areas of theory is highlighted, and promising directions for future research are outlined. Cutting‐edge work deals with new ways to conceptualize and measure moral identity, mechanisms of influence, links to broader outcomes, situational variation in moral identity, and implicit aspects of moral identity. Promising future directions are expanding on these emerging directions, as well as looking at developmental processes, cultural variability, and the role of relationships.