This chapter considers the legitimacy authority of global human rights institutions, the right to have the final say on a question of human rights. It shows how human rights was transformed from a moral code to a set of binding international law obligations in the aftermath of the 1960 Sharpeville Massacre, allowing a role for ‘Charter bodies’ and ‘Treaty bodies’ to monitor the human rights situations in states. The main Charter body is the United Nations Human Rights Council; the 9 core human rights treaties each have their own bespoke Treaty body, although these operate in similar ways. The work focuses on the interpretive authority of the Treaty bodies, which depends on the acceptance of that role by the states parties, a form of sociological legitimacy. This in turn relies on a recognition of their normative legitimacy, understood variously in terms of the Treaty bodies working within the constraints of the rules for interpretation in the Vienna Convention on the Law of Treaties (legitimacy as legality), the need to adopt a pro homine (‘in favour of the individual’) approach to interpretation (welfare enhancing, or output, legitimacy), the requirement to show the positions of the Treaty bodies are the result of their expert knowledge, following review of the states parties’ reports (epistemic legitimacy), and that Treaty bodies reach their conclusions in a considered manner (procedural legitimacy). The chapter concludes that the legitimacy authority of the Treaty bodies depends on their ability to persuade, not to command.