Animals are integral to world politics, yet largely neglected in International Relations (IR). This Special Issue (SI) aims to address this gap and offers a collection of original research articles that investigate issues pertaining to sovereignty, power, diplomacy, the ethics of war, justice and emancipation, environmental governance, activism and international law. The articles make animals visible within those realms, raise novel questions and develop approaches through which the specific role(s) of animals and human-animal relations in international politics may be theoretically understood and empirically explored. They open a conversation between IR and Critical Animal Studies (CAS). The SI contributes to a broader understanding of the complex and interconnected nature of human-animal relations, and therefore to the reorientation of IR towards a post-anthropocentric perspective of world politics that renders the field better equipped to understand and address our current Anthropocene predicament. To introduce the SI, this article starts by addressing the invisibility of animals in IR and why this is problematic. It then provides an overview of the articles included in the SI and concludes by outlining a research agenda for the study of animals in IR.