In this chapter we focuse on non-state actors as perpetuators of political violence. In particulare we focus on organized and higher-level forms of political violence, rather than on smaller-scale and less organized forms of violence that occur during street demonstrations or in the form of riots. Yet we explicitly emphasize that different forms of political violence are interlinked and are part of a continuum of violent tactics – rather than representing discrete and mutually exclusive types – and often occur successively or simultaneously during processes of escalation. We introduce how social movement scholars have during the past decades approached and analyzed political violence introducing a perspective which entails the contextualization of the phenomenon. We also trace the development of the field in cognate areas of research dealing with political violence, such as: terrorism studies, research on militant Islamism and civil. In the concluding section we will suggest a possible direction for future research on political violence recognizing the achievements produced so far from the social movements field.