This chapter explores the value of and bases for police legitimacy. In doing so, it distinguishes between descriptive (or perceived, popular) legitimacy, and normative legitimacy, ultimately arguing that the latter is the natural ground of democratic policing and the more critical of the two, given policing’s commitment to practical, substantive justice. One of the principal hazards of descriptive legitimacy is its ability to yield a popular perception of policing’s legitimate authority that can sanction populist sentiments, ones that do not necessarily protect minority rights or honor a commitment to pluralism. Legitimacy is critical in the police pursuit of cooperation, especially in times of epistemic uncertainty, and the argument here is that the careful pursuit of substantive justice that conforms to the requirements of normative legitimacy will yield descriptive legitimacy across a substantial part of the community, and especially among its more marginalized or vulnerable members.