This chapter presents sovereignty as a normative principle but, in so doing, will also explain its descriptive aspect. The first part of the chapter connects sovereignty to an account of the state. Sovereignty captures two groups of elements that are necessary features of this institution: on the one hand, the characteristic authority claims made by the state; and, on the other, the demand that these claims be—to some extent—effective. The second part of the chapter considers the importance of sovereignty: the moral reasons that we have for creating institutions that possess its characteristics. Third, the chapter considers whether there are some situations in which sovereignty is unattractive or, perhaps, situations in which non-state institutions are preferable locations for sovereignty. The chapter concludes by arguing that for the vast majority of people today, sovereignty is of significant moral value.