The punitive turn in criminal justice policy, epitomized by policies like three-strikes, truth in sentencing, and mandatory minimums, is often attributed in part to demand for harsher criminal justice responses from an increasingly punitive public. It has been argued that public opinion, known to be both largely uninformed and often misunderstood, might both indirectly and directly affect policy. This survey article on punitiveness in public opinion opens with a discussion of competing depictions of the nature of the relationship between a punitive public and increasingly punitive criminal justice policies. The article then focuses on some of the most influential explanations for variations in punitiveness within individuals and across groups. A review of what we know about public attitudes toward punishment and a brief explanation of how we know what we know (e.g. the methodologies by which we gauge public opinion) follow. The article concludes with the observation that as methodologies continue to improve and the literature in this area continues to grow, so too does our understanding of punitive public opinion in all of its complexity.