The World Social Forum (WSF) is the world’s largest activist network to date. Its global, regional, national, and thematic events have gathered since 2001 millions of participants and thousands of civil society and social movement organisations. Its cosmopolitan vision is built on resistance to the planetary domination by neo-liberal globalisation. This paper unpacks WSF’s cosmopolitan project and reflects on its vision of emancipated individuals, convivial communities, and a just planetary society in harmony with the environment. In its open organisational space, WSF’s cosmopolitan project develops while in the process of political action rather than prior to that. At the same time, power dynamics, ideological cleavages, and pragmatic concerns about organisation and strategy challenge WSF’s ability to pursue its goals. However, it is these internal tensions that make WSF’s cosmopolitan project both more difficult to achieve and more realistic than claims of universal unity among all its participants. [ABSTRACT FROM PUBLISHER]