This article examines the practical and theoretical implications raised by protesters' use of masks to conceal themselves from the eyes of the state. It argues that the refusal to be seen and categorized by the state is empowering in that it exposes, and then unsettles, the power dynamics that have traditionally structured public space. It analyzes the different ways in which masks create transformative in-between spaces that signify the presence of a deliberately unspecified absence and therefore facilitate the possibility of thinking differently. It concludes that this strategic form of presence reveals the usually invisible boundaries of the public sphere and, in doing so, renegotiates the dynamics of power that have structured articulations of dissent. These issues are explored through an analysis of the masks worn by the Zapatistas, the Black Bloc, carnivalesque protesters, antiwar protesters, and the Occupy movement.