Chapter 5 addresses legitimacy as both a consequence and a source of depoliticization based on case studies essentially in the fields of economic and human development, environmental protection, global health and regulation of multinationals. First, it explores how depoliticization contributes to legitimation processes: depoliticization practices help gain recognition to preserve and expand IO mandates by suppressing the opportunity to question their legitimacy. Gains in legitimacy may thus justify depoliticization practices. Second, the chapter analyzes the reversed process by which legitimacy claims have depoliticizing effects: as a result of a monopolized legitimacy acquired by an IO, alternative actors, policies and multilateral arrangements are overlooked, if not entirely delegitimized. By institutionalizing a monopolistic position, IOs exclude alternatives and limit space for debate.