This thesis analyses the conditions for the promotion of ecological citizenship, using the tools of political theory. I examine the role of the state, the green state, the green public sphere and civil society in the articulation of ecological citizenship. The dominant position in this debate is that states should be actively involved in the greening of citizenship, using different strategies to encourage ecological habits and values among citizens. These possibilities are analysed and assessed. Some have argued, drawing on studies of the ecological reform of the state, that in order to foster ecological citizenship, states should undergo transformations so as to become green states. This view is examined with a focus on the difference between the liberal state and the green state in order to clarify the distinct conceptions of ecological citizenship that they uphold, and the variety of mechanisms and institutions used by each of them to articulate ecological citizenship. Although the green state offers more opportunities for the promotion of ecological citizenship, some of the problems of state-centric approaches persist, so the discussion moves onto actors and spaces outside state institutions. This part of the research starts with a discussion of the notion of the green public sphere and investigates how ecological citizenship may be defined within this sphere. This analysis concludes that a conception of the green public sphere different from that which dominates the eco-political literature is required both for the promotion of ecological citizenship and a politics of sustainability. To this end, I suggest a redefinition of the green public sphere. Finally, after distinguishing between the public sphere and civil society, I examine the possibilities of nurturing ecological citizenship in civil society.