The proliferation of lone-actor terrorist attacks over the past decade has led to a rapidly expanding literature and a subfield of research. However, this research has only to a limited degree been brought into wider discussions on political violence and social movements. In the present article, we take up this synthetic challenge and argue the need to theorize the social and collective dynamics of lone-actor terrorism. The article proposes a novel analytical framework for understanding lone-actor terrorism. We provide a conceptualization that draws attention to the social embeddedness of terrorist lone-actor radicalization and the collective dynamic of lone-actor attacks. Our point of departure is the recurrent finding that lone-actor terrorists are in fact not that alone, and that their attacks tend to cluster in time and space. First, we propose to conceive of lone-actor radicalization as a relational pathway shaped by social ties and interactions with radical milieus/movements. Second, taking inspiration from Charles Tilly's notion of "scattered attacks"as a pattern of dispersed, loosely coordinated collective violence, we suggest three complementary ways of analyzing these processes and their temporal and interactive dynamic. We argue that theorizing the social and collective dynamics of lone-actor political violence is not only about addressing an empirical puzzle (the abundance of social ties; the clustered pattern of violent attacks), but about analytically capturing an entirely different and potentially increasingly relevant logic of violent processes. Thereby, and paradoxically, the very notion of "lone actors"can help us to understand the social dynamics of collective political violence more generally.