This chapter offers a general theory of institutional legitimacy, the Metacoordination view, according to which legitimacy assessments are best understood as being part of a social practice aimed at achieving consensus on whether an institution is worthy of our moral reason-based support—support not dependent solely on the fear of coercion or on a perfect fit between our own interests and what the institution demands of us. The Metacoordination view’s account of the practical function of legitimacy assessments is used to identify criteria of legitimacy that apply to a wide range of institutions and to show that, for institutions that back their rules with coercion, conformity to the requirements of the rule of law is a presumptive necessary condition of legitimacy. The Metacoordination view is shown to be superior to consent theories of legitimacy and attempts to use Raz’s “service” conception of authority as an account of institutional legitimacy.