Despite a recent turn towards the study of political violence within the field of contentious politics, scholars have yet to focus their lens on genocide. This is puzzling, as the field of collective action and social movements was originally developed in reaction to fascism (Nazism in particular), while research on collective action and research on genocide have long shown parallel findings and shared insights. This paper reviews the history of this scholarly convergence and divergence, and suggests that recent findings of research on genocide can be improved by the consideration of concepts from social movements and collective action. It then details three theories of the micro-mechanisms that mobilize individuals for contentionframing, diffusion, and networks -and specifies how they refine existing explanations of civilian participation in genocide. In the conclusion, I suggest that a contentious politics approach to genocide would consider it one form of collective action among others, analyzable within the existing framework of collective action and social movement theory.