The relationship between power and resistance behind prison walls has long animated sociological discussions of imprisonment. In this article we advance a fresh understanding of resistance that recognizes the multi-faceted dimensions of prisoner agency while acknowledging the dangers in simply valorizing the strategies of the confined to subvert penal power. For us the importance of resistance is that it makes explicit the connections between everyday actions and broader inequalities. Nevertheless we identify three limitations in conventional characterizations of resistance. First it is understood as a privileged quality in the human spirit. Second, is the assumption that those who do not challenge authority accept the legitimacy of the institution. Third is the equation of resistance with rudimentary political action. Though drawing on our empirical research conducted in male and female prisons in the UK we refine the concept to overcome these limitations. In particular we indicate how social identities mediate prisoner agency and are crucially implicated in acts of contestation. Our more general ambition is to place at the centre of prison sociology the still marginalized issues of gender, race and sexuality.