This chapter examines the role of non-governmental organizations (NGOs) in world politics. It considers what distinguishes NGOs from other actors in international politics, what types of influence NGOs exert in international relations, and whether NGOs contribute to more democratic policy-making at the international level. The chapter also discusses the growing importance of NGOs and presents two case studies that illustrate how they have contributed to the emergence of new norms through their engagement with international governmental organizations (IGOs): the first is about campaigns run by transnational NGOs to end violence against women and the second is about their climate justice activism. There is also an Opposing Opinions box that asks whether transnational NGOs contribute to more democracy at the international level.