When is the authority of the state legitimate? In my research, I will investigate recent ‘realist’ attempts to answer this question. Realist accounts of legitimacy ground legitimacy in citizens’ acceptance or approval of rule, which distinguishes them from accounts of legitimacy based on consent or rational acceptability. These realist theories, so called to emphasise their rejection of deriving normative conclusions from abstract principles of reason, have considerable advantages. They account for the intuitively plausible ideas that legitimacy depends on the beliefs and attitudes of those subject to rule, and that the criteria of legitimacy vary across cultural and historical context. My thesis will explore to what extent realist legitimacy can answer the ‘puzzle of legitimacy’ – namely, how some people come to acquire the right to rule over others – but also ask whether realists need accept this formulation of the puzzle in the first place.