This themed issue provides an international perspective on transnational processes in digital activism and protest. Against wider claims that social movements and citizen activism are shifting from the logic of spatial organization to networked flows, this themed issue foregrounds the interplay between the global and local in networked public spheres. Recent transnational movements such as #MeToo or Black Lives Matter yield the importance of interweaving digital communication, pre-existing activist collectives, and citizen activation on a seemingly global scale. In this Introduction, we ask how political causes circulate globally, what role digital technologies play, and ultimately, what "transnational" means for seemingly universal causes, global collective identity, and activist practice. After providing an overview of the different theoretical insights that an interdisciplinary approach to digital activism can provide, we outline a conceptual framework for approaching the transnational as an entanglement of flows, hierarchies, and agencies.