This article reviews the international evidence on the potential nature, sources, and consequences of police and legal legitimacy. In brief, I find that procedural justice is the strongest predictor of police legitimacy in most of the countries under investigation, although normative judgements about fair process may—in some contexts—be crowded out by public concerns about police effectiveness and corruption, the scale of the crime problem, and the association of the police with a historically oppressive and underperforming state. Legitimacy tends to be linked to people's willingness to cooperate with the police, with only a small number of national exceptions. There is also a fair amount of evidence that people who say they feel a moral duty to obey the law tend also to report complying with the law in the past or intending to comply with the law in the future. The main argument is, however, that international enthusiasm for testing procedural justice theory is outpacing methodological rigor and theoretical clarity. On the one hand, the lack of attention to methodological equivalence is holding back the development of a properly comparative cross-national analysis. On the other hand, the literature would benefit from ( a) greater delineation between legitimation (the bases on which citizens judge the rightfulness of an institution) and legitimacy (the acceptance or rejection of the rightfulness of an institution and the normatively grounded duty to obey), ( b) stronger differentiation between police and legal legitimacy, and ( c) more attention given to isolating the mechanisms through which rightfulness and consent motivate cooperation and compliance.