Transboundary and global environmental harm present substantial challenges to state-centered (territorial) modalities of accountability and responsibility. The globalization of environmental degradation has triggered regulatory responses at various jurisdictional scales. These governance efforts, featuring various articulations of state and/or private authority, have struggled to address so-called “accountability deficits” in global environmental politics. Yet, it has also become clear that accountability and responsibility norms forged in domestic regulatory contexts cannot simply be transposed across borders. This special issue explores various conceptual perspectives on accountability and responsibility for transnational harm, and examines their application to different actor groups and environmental governance regimes. This introductory paper provides an overview of the major theoretical positions and examines some of the analytical challenges raised by the transnational (re)scaling of accountability and responsibility norms.