Global Civil Society. Shadows and Light - This essay comes in two sections. First, the various definitions of « global civil society » found in the contemporary debate are examined, as well as some theories thereby inspired. In its most widespread meaning, the expression « global civil society » designates a heterogeneous set of movements and associations, transnationally organized, that are held to represent the dawning of a « global public sphere ». The second section of the essay discusses some empirical cases regarding the actors of global civil society: the coloured revolutions in eastern Europe, the no-global demonstrations in Seattle and Genoa, the social and humanitarian interventions of international NGOs. Extremely diversified results can be registered: spontaneous groups and organisations with clear-cut management styles, associations grounded on voluntary or professional work, protest movements and NGOs advising the WTO or the EU. Governance-focused theories look with increasing interest at these actors, since they seem able to reduce the legitimacy deficit that affect international institutions. The author expresses some critical considerations on this issue, stressing the risk that subaltern cooptation at the service of politics might prevail in the associations of civil society.