The recent uptake of the concept of transboundary commons has directed attention towards the complexities of cross-border environmental governance. Transboundary commons are broadly defined as the spatial arrangements for governing shared resources and coordinating responses to environmental threats and crises that traverse jurisdictions and property boundaries within, as well as between, nation-states (Giordano, 2003;Hirsch, 2020;. Etymologically and genealogically, transboundary commons inscribe a specific set of relationships that value resources 'in common' across borders. Scholarship on the global commons and transnational commons has focused on the international dimensions of dispersed and overlapping resource regimes (Holder and Flessas, 2008;Corson and MacDonald, 2012). While sharing many characteristics with these allied concepts, the notion of transboundary commons does not restrict the study of cross-border relations to national-level units of analysis but extends to encompass all scales of environmental governance. As such, the analytical lens of transboundary commons prompts critical reimagination of the myriad connections between place-based forms of resource organisation and distant decisionmaking processes, labour, technologies and markets that shape (re)distributional outcomes within and among countries.This special issue is concerned with increasing the understanding of the challenges and opportunities involved in governing environmental issues that are cross-jurisdictional and multi-scalar in nature. By definition, the transboundary commons problem cannot be addressed by individual groups of resource users, sectors or administrations. Common environmental goods, such as biodiversity, regional