AbstractThis chapter examines the relationship between knowledge and Environmental Citizenship. Knowledge has been attributed to have an essential role in influencing pro-environmental behaviour and as such in the development of Environmental Citizenship. We argue that the ‘right’ kind of environmental knowledge is a necessary precondition for pro-environmental behaviour and thus for Environmental Citizenship. In this chapter, we focus on knowledge, but we also emphasise that efforts on fostering knowledge alone in education for Environmental Citizenship, without links to real life, competencies and values, are insufficient for the sake of a sustainable world. We explore which knowledge is needed in order to cultivate the coherent and adequate skills, values, attitudes and competences that we think an Environmental Citizen should have. We identify three different types of knowledge: (i) environmental systems knowledge, (ii) action-related knowledge and (iii) effectiveness knowledge. Finally, we suggest a process of co-production of new knowledge between experts and key citizens as central to the idea of a participatory approach towards developing Environmental Citizenship.