This chapter reviews the literature on how digital information technologies are changing the ways that social movements form, organize, and mobilize. We draw on social movement scholarship, STS, and media studies to trace the conceptual gaps that have emerged as a result of different pathways of theorizing the intersection of activism and social movements with digital technologies. We argue that the social movement perspective remains theoretically underdeveloped because of its limited understanding of the cultures and situated use of technology, as well as a narrow focus on mobilization that takes identified movements as its starting point. STS in turn has paid relatively little attention to activism and social movements. Much of the STS literature treats technology and social movements as separate domains, explaining how technology is either the object of activism or the outcome of activist innovation. New media and communication studies have emerged as the fastest growing discipline investigating digital technologies and their use by movements – but with their own theoretical limitations. We point to fruitful attempts to integrate knowledge and theory from these different disciplines and spell out an agenda for further closing the conceptual and empirical gaps in our knowledge about movements and (digital) technology.