Tracing the work of three community-engaged theatre projects in different UK urban contexts, this thesis considers the ways in which contemporary theatre might constructively and proactively engage with and mobilise community as a progressive political force. Set against sociologist Zygmunt Bauman's contention that, in the context of contemporary neoliberal society, community can no longer be seen to reflect a realistic model of social relations but, rather, a symbolic articulation of 'everything we miss and what we lack to be secure, confident and trusting', I consider ways in which theatre could be understood as a performative framework through which different models of interrelational praxis and productivity might be imagined and realised. In dissociating community, as it is implicated in the practice of theatre, from an inherent relationship to social context as it exists outwith or beyond theatre practice, I draw attention to the contingent relationship between the circumstances in which theatre takes place and the modes of social, cultural or political agency that might be associated with its practice. I argue, in particular, that contemporary efforts to mobilise theatre as a political force are required to articulate ideological ambitions through and, at times, in collaboration with the systemic conditions in which they operate, even when those conditions represent values, practices or ideals that appear contrary to theatre's progressive aims. It is from this perspective that I argue for a model of practice that overlooks representational or epistemic registers of affect to privilege an ontologically informed measure of relational praxis, agency and politics. Framed by a consideration of the history and development of community theatre since the late nineteen-sixties, I attend to three contemporary case studies that sit within the rubric of community, socially-engaged or participatory theatre: The Create Course, a collaboration between the Battersea Arts Centre, the Katherine Low Settlement and lead artist Naomi Alexander that took place in London and, over eight weeks, aimed to replicate the praxis of socio-political action framed by theatre maker Joan Littlewood's imagining of a Fun Palace. Albert Drive, led by Glas(s) Performance, which took place in Pollokshields, Glasgow and, over the course of eighteen months, sought to engage residents in a shared consideration of neighbourliness, and the ways in which this connection might be leveraged to influence the socio-affective environment in which they lived. And, Seeing Red by Melodramatics, a drama group that emerged out of a partnership between the Octagon Theatre, Bolton and social housing charity Bolton at Home, who sought to mobilise theatre to address issues of domestic abuse in the Farnworth area of Bolton. Methodologies differ depending on the circumstances of the practice, however, all projects were studied in the field and most studies are based on observation over several months, in-depth, qualitative interviews with artists and participants, and combine elements of discourse and performance analysis.