Summary: In 415 words the entry focuses exclusively on state sovereignty, it highlights the importance of the transition from statehood based on territory alone to statehood based on national identity, and it contrasts the principle of state sovereignty with the reality of international relations in the second half of the twentieth century. Constitutional and international law understand state sovereignty as the exclusive and legitimate power of the state vis a vis domestic actors and other states. This power rests originally with a monarch or dictator and in democracies with the parliaments. The entry highlights that with the development of internationally aggressive forms of nationalism and great-power politics, sovereignty functions as a defense clause for weaker states. International organizations, operating mostly on the consensus principle rather than majority rule, have been established to institutionalize this defense. While in principal all states are equal, the entry strengthens the reality of international relations, where on the one hand absolute state sovereignty was always fictitious and on the other the solution of structural and actual problems increasingly demand cooperative bargaining and compromise. Furthermore, as the entry concludes, in the late twentieth century state interdependence increases and international organizations and powerful non-state actors increasingly pose challenges to the ideal of absolute state sovereignty and national self-determination.