This article argues for a citizen social science methodology in which residents from the sites of inquiry play a central role in key activities of the research process and beyond: research design and data collection, presentation and publication of findings, and design and implementation of urban interventions that address challenges to quality of life. This is a way of democratising the research process through sustained engagement with communities and an emphasis on co-designing pathways to impact. The article draws on the authors' experience of running a citizen social science project in Beirut, Lebanon, where citizen scientists, university academics, and NGOs have worked collaboratively to understand what prosperity means for local residents, develop context-specific measures of prosperity, and design and implement small-scale interventions for local challenges.