‘Environmental Citizenship’ is an intervention in a growing body of scholarship that seeks to redefine what it means to be a citizen – not merely of a nation, but of a planet. The contributions to this collection frame environmental citizenship as a plural, relational, and deeply political practice that, as its history unfolds, must continually reckon with its own exclusions in order to imagine sustainable and more just futures. Regarding environmental citizenship as an evolving conceptual framework, one that extends beyond anthropocentric, Euro-American, and state-centered paradigms, the essays in this volume respond to the need to ground the concept in relational thinking – across species, geopolitical boundaries, and academic disciplines – in order to reconsider what it means to act, belong, and care within a more-than-human world.