The banlieues (suburbs) of Paris are key case study for the social and political evolution of post-war France. Drawing on the overarching narrative of the trente glorieuses, existing scholarship has viewed the construction of grands ensembles d’habitation (mass housing estates) as part of a harmonious modernisation project through which France moved away from governing its colonies and towards the governance of everyday life. Yet, this view of banlieue housing as an expression of generic, totalising state power overlooks the conflicts and uncertainties that underpinned the modernisation process. This thesis analyses the construction and governance of two grands ensembles: the 4000 logements in La Courneuve and Les Courtillières in Pantin during the period 1955-1973. By analysing how state actors constructed and debated notions of urban modernity, this thesis will use the grands ensembles to explore France’s post-war modernisation as an uneven, localised and limited process. In discussing the limits to state power in these areas, this thesis develops scholarship on the banlieues and post-war France in three key ways. Firstly, this thesis will interrogate the relationship between the grand ensemble and notions of modernity, and will challenge the notion of mass housing as part of a forward-thinking modernisation process. Close analysis of sociological studies of mass housing and planning discourse will be used to demonstrate that the key objective was not to modernise, but to create a benign governable space that glossed over the more complex reality. By looking at localised discourses of municipal council and housing associations, this thesis will also question the harmonious nature of modernisation in discussing the ongoing debates between different state actors regarding the role of mass housing and of the banlieues more generally. Secondly, this thesis will develop academic understandings of the relationship between the citizen and the state. While the banlieues have been situated within the orbit of a totalising, technocratic Gaullist national state and the local communist-governed municipality, this thesis will question whether the state ‘existed’ in the banlieues. Records of municipal campaigning and existing resident testimonies will be used to challenge the historical narrative of the ceinture rouge by demonstrating that at a local level, the state maintained only loose control in the governance of everyday life and focused on a narrow range of issues. Developing this notion of a flexible, arterial state, this thesis will also analyse estate plans closely in order to highlight that interior space rather than enacting new forms of social conditioning was uneven in nature and made considerable concessions to existing modes of living. Thirdly, this thesis will develop existing notions of power and authority by arguing that while French post-war modernisation has generally been viewed as a technocratic process, it relied on direct coercion to compensate for its inherent limitations. While scholars have viewed the grands ensembles as a short-lived triumph of ‘the liberal art of government’, this thesis will argue that technocratic governance of the banlieues was ‘propped up’ by a dramatic expansion of policing and surveillance of these areas. This thesis will analyse police records of racial and geographical profiling and the suppression of protest in order to argue that policing produced a more systematic form of banlieue governance compared to uneven, limited technocratic power. Overall this thesis will use the grand ensemble to present an alternative view of the trente glorieuses in which the French state projecting authority into areas where the state lacked knowledge or influence, and sought to protect itself from modernity rather than to enact it.