Social movements are builders of what are known as “grammars of democracy”, that is, val-ues, participatory experiences, political cultures, languages and structures for articulating demands. This article analyses the 15M or indignados (outraged) movement in Spain; a collective action that went be-yond classical protests in response to the economic crisis and proposed changes in democratic practices. Social movements, particularly from the 1990s onwards, have focused on democracy as both a means and an end in order to address what they perceive as authoritarian globalization. The article approaches 15M mainly as a space for mobilization articulating the heterogeneity of the movement as well as its effects in Spain (anti-eviction struggles, PAH, social tides, etc.) with a direct reference to the master frame of 'radical democracy'. Methodologically, this work is based upon interviews, focus groups and participant observa-tion conducted from May 2011 to June 2012 during the occupation of public squares and subsequent mo-bilizations. The text situates this phenomenon in the core of the New Global Movements, and connects it with a decade of similar collective actions in Spain and other parts of the world. Finally, aspects such as the role of the Internet as a tool for and driving force of new models of democracy and the scale of assemblies in relation to deliberative democracy are also discussed.