International institutions have developed into a site of political authority of their own as can be seen by looking at a number of authority indicators. The concept of international authority, however, is intimately bound to the concept of legitimacy. The stronger the role that international institutions play in policymaking, the stronger the demands for their legitimacy that can be expected to arise. Against this background, we ask which of the state powers analysed in this special issue prefer which form of legitimation of international institutions, whether their general conceptions of legitimacy diverge or converge, and what this means for the future of global governance.