A vast scholarship shows that social movements can play pivotal roles in bringing about policies that benefit marginalized groups. However, the role of social movements in entrenching those policies—ensuring they take root—remains insufficiently studied. We set a research agenda for the study of how social movements shape policy entrenchment by calling attention to three commonly used strategies—occupying state bureaucracies, engaging in pressure and persuasion tactics, and building alliances with political parties—and analyzing the relationships among them. We illustrate these strategies through short case studies of social movements that achieved significant change benefitting marginalized groups in Latin America: the health movement in Brazil, the unemployed workers’ movements in Argentina, and peasant and indigenous movements in Bolivia.