ABSTRACT Living with cultural, religious, and ideological diversity inevitably creates situations where people are confronted with beliefs, values, or practices that they disapprove of. In such situations, people may consider reasons to nevertheless tolerate what they disapprove of (i.e., forbearance tolerance), or reject these (i.e., intolerance). In the current review, we consider empirical research on the processes of intergroup tolerance and consider different manifestations of (in)tolerance. Then we discuss recent work on the dual process model of tolerance, which considers intuitive versus deliberative objections to cultural, religious, and ideological differences, and how these can be overridden to produce tolerance. We then review literature on the boundaries of tolerance including the role of moralization and moral values, before considering individual difference factors and situations of threat that can hamper intergroup tolerance. We conclude by considering five areas ripe for future exploration on the social psychology of intergroup tolerance and intolerance.