This document presents the role of social movements in health sector accountability, based on lessons learned by the Health NGOs Network (HENNET). Social accountability means holding public officials to account for the delivery of health services, and supports universal health coverage. Social movements are groupings of individuals and organizations that mobilize collective action to bring about change. The case of HENNET illustrates how a unifying platform, structured as a national network and county sections, coordinates over a hundred organizations, improves the dissemination of information, avoids duplication and mobilizes resources. HENNET influences policy by participating in technical working groups, endorsing strategies and supporting innovations in maternal, newborn and reproductive health. Approaches implemented include the development of service charters to inform users, community awareness-raising, the use of information technology to enhance data transparency, and capacity-building for monitoring and dialogue with providers. The network prioritizes peaceful engagement with government, while organizing public actions when necessary. Successes include influencing government decisions, replicating local approaches and extending the model to other countries. The text concludes that social movements, by strengthening citizen voice and multi-sectoral participation, are key levers for improving accountability and moving towards universal, equitable and sustainable health coverage.