As the United Nations has developed and as its role in world affairs has been adapted to the necessities and possibilities created and the limitations established by the changing realities of international politics, collective legitimization has emerged as one of its major political functions. By this I mean to suggest that the world organization has come to be regarded, and used, as a dispenser of politically significant approval and disapproval of the claims, policies, and actions of states, including, but going far beyond, their claims to status as independent members of the international system. In this essay I shall undertake to refine and elaborate this rough definition of collective legitimization and to discuss the performance of this role by the United Nations. It is essential in the beginning, however, to provide a foundation by offering some observations about the general problem of political legitimacy.