This chapter is a theoretical attempt to study the multifaceted authority of the European Union (EU) in world politics. Authority is legitimated power. Without legitimacy, power often faces severe resistance whereas legitimate actions and actorness imply less opposition if not widespread support. Informed by the thesis of Steven Lukes on three-dimensional power and Mark Suchman’s trichotomy of legitimacy, this chapter advances three dimensions of the EU’s authority in the world and discusses how the EU could maintain and/or restore its legitimacy in the global arena.