The UN's Sustainable Development Goals (SDGs) have been conceived as a global roadmap for peace, dignity, and prosperity on a healthy planet (UNDP 2016). The SDGs challenge the dominant notion of prosperity as material wealth measured by GDP and rising household incomes; instead prosperity is reframed as a shared condition to be weighed alongside ending poverty, tackling inequalities, and safeguarding the environment. Cities are identified as having a critical role in generating and equitably distributing prosperity on these terms. Reframing prosperity in this way opens up space for new forms of dialogue about what it means for people everywhere to prosper, asking how material wealth, other forms of value, equity, and fairness, and the needs of humans and nonhumans are differentially understood and acted on. Yet this article argues that prosperity is understudied and undertheorized by social scientists. A new research agenda, driven by empirical studies in diverse urban contexts, must form the basis for new theoretical insights and policy formation that will drive action on prosperity in the years to come. Presenting new empirical work from community‐led research in three east London neighborhoods, the article examines prosperity as a lived experience in comparison to policy goal, demonstrating how context‐specific meanings and practices challenge the orthodox models and metrics that currently dominate policymaking. The authors demonstrate how situated and engaged research with local residents and citizen scientists provides the basis for developing new prosperity metrics that reflect issues of specific value and concern to individuals and communities in east London.