Urban informality is typically ascribed to the urban poor in cities of the Global South. Drawing on Judith Butler's concept of performativity and taking the case of Rio de Janeiro in the context of the 2016 Olympic Games, this article conceptualizes informality as a signifier and a procedural, relational category. Specifically, it shows how different class actors have employed the signifier informality (1) to legitimize the confinement of marginalized populations; (2) to justify the organized efforts of the upper middle class to protect their 'self-enclosed' gated communities; and (3) to warrant the formation of opposition and alliances between inhabitants, activists, and researchers on the edges of the urban order. This article offers new perspectives to better understand the relationship between informality and confinement by examining the active role that inhabitants of marginalized settlements assume in the Olympic City.