This chapter outlines the major theoretical frameworks, research trajectories, and conceptual developments in the social psychological study of justice over recent decades. Justice theory and research in social psychology have centered on several fundamental questions: what is justice? What is considered fair or unfair in different contexts? What criteria do individuals use to guide just behavior and evaluate whether justice has been served? When does justice become salient? Why does justice matter? Under what conditions, and for what reasons, do people become concerned with justice? How are justice-related evaluations shaped? What behavioral and cognitive responses are triggered by experiences of injustice? And what are the consequences of perceiving justice or injustice? The answers to these questions are presented through a discussion organized around the following key insights: (1) conceptualizations of justice: including rights and duties, and the three primary forms of justice judgments—interactional, procedural, and distributive justice; (2) outcome-focused versus relationship-focused paradigms in justice research; (3) the formation of justice judgments, with particular attention to the notion of overall justice; (4) motivating and motivated cognition: exploring the causal relationships between perceptions of fairness, beliefs, attitudes, and behavior; (5) contemporary perspectives on social justice, with a special focus on recognition justice.