This dissertation is a social history of the Uganda Prisons Service in the late colonial and early post-colonial periods. Focusing particularly on prison officers, it advances four key arguments. Firstly, it argues that global visions of the prison were crucial in shaping the Service’s development, its institutional culture, and the professional identities of its personnel. From the late colonial period onwards, this vision was anchored on notions of penal welfarism, which positioned the prison as a centre of rehabilitation, staffed by professionals who possessed technical expertise. Secondly, the penal welfare model was combined with an emphasis on the prison’s role as a driver of economic development and a source of public revenue – features that were seen as compatible with penal modernity. Thirdly, this vision of the prison gave the Service a particular imaginative capital, which prison officers used as an important resource. It provided them with a common set of principles and norms through which to define their professional role. Senior officers adopted it with alacrity, pursuing further professionalization through engagement with transnational penal reform networks. Others summoned it as a source of claim-making, using it to call on the state to provide them with greater benefits and treat them as respectable public servants. Finally, visions of penal modernity and professionalism were contested throughout the periods under study, leading officers to engage in boundary work. Officers were regularly defining their role in relation to other spaces of incarceration, such as local government prisons and informal detention sites. With the take-over of Idi Amin in 1971 and the militarization of the state, prison officers’ professional identities were profoundly challenged, but also became particularly important, providing them with a conceptual boundary that at least partially demarcated them from Amin’s regime. Ultimately, the case of the Uganda Prisons Service reminds us of the importance of studying prisons beyond their coercive capacities, paying attention to how such institutions became the focal point of debates over modernity, authority, and professionalism. More broadly, this study challenges the narrative of failure that has dominated popular and scholarly portrayals of state institutions on the African continent, rejecting generic depictions of the postcolony as a site of chaos and disorder.