This chapter considers the deep and complex relationship between urban commons and conflict. These sites have been both the setting for protest and the subject of contestation. Drawing on recent research concerning conflict and space, this chapter argues that the prevalence of conflict in and over urban commons is a direct consequence of their peculiar character. They are empty spaces offering potential for multiple users to inhabit, use and imagine the space in their own ways and provoking attempts by authorities and users to codify and control them. They are enduring spaces that have existed over time and retain evidence of past uses within the landscape. Yet this also means that the legal frameworks that protect them can be at odds with the lived reality of these spaces. Consequently, they are enigmatic spaces, the meaning of which is not fixed but open to a multiplicity of interpretations. As a result, conflicts can emerge between users who have different visions of the common and use it for different – sometimes incompatible – purposes.