There is currently a shift towards embracing 'structural intervention' approaches in HIV prevention and HIV treatment. We offer the concept of hope as an important new framework for researching HIV prevention and HIV treatment. We argue first, that hope is linked to capacity for behaviour change and helps us understand how social environments enable as well as constrain risk reduction. Second, we argue that hope helps us understand HIV treatment engagement and impact, especially uneasy relations between treatment access expectation and the lived experience of treatment delivery in environments characterized by fragile treatment systems. We conclude that HIV prevention should seek to create the structural conditions conducive to sustaining hope in the future, while drawing attention to the often unforeseen local effects of global discourses of HIV treatment promise which may offer an illusion of hope in certain contexts. We draw specific attention to the urgent need for interventions to tackle the adverse psychological and social consequences of fragile treatment delivery. Hope is an under researched concept in the social science of HIV prevention and HIV treatment. It offers unrealized potential, particularly for thinking about structural interventions in relation to managing HIV as a chronic illness and for maximizing HIV risk reduction in resource-poor settings.