Global governance in many domains is increasingly characterised by the existence of international regime complexes—i.e., sets of overlapping institutional fora taking up different aspects of a broader issue area. As an international actor, the EU faces a context of such international regime complexity. Yet, little is known about how the EU navigates international regime complexes and how regime complexes impact the EU’s behaviour in individual fora. This thematic issue, therefore, seeks to improve our understanding of how different manifestations of international regime complexes affect the EU as an international actor and to provide empirical insight into the ways actors like the EU navigate international regime complexes. In this editorial, we situate the thematic issue within the broader academic debates on the EU’s role in international regime complexity, argue for the need to study the EU as an actor therein, and provide an overview of the thematic issue’s objectives and the nine articles that comprise it.