Across the globe, movements are confronting states and elites, challenging inequalities and mobilising for greater justice, a stronger voice, and progressive policy changes. In this article, I bridge the divide between Social Policy and the interdisciplinary field of Social Movement Studies. I examine how and why social movements, as actors in policy fields and social movement theories, matter for social policy. I argue that research on social movements as actors and engagement with social movement theories can open new horizons in Social Policy research by advancing our understanding of the politics of policy from a global perspective and strengthening our analytical and explanatory frameworks of agency, ideas, and power in the study of continuity and change of policy.