European cities face a pressing challenge - how can they provide economic prosperity and social cohesion while achieving environmental sustainability? In response, new 'living labs'- sites devised to design, test and learn from social and technical innovation in real time - are being formed. Individual cases have been studied, but limited work has been done to understand how they work across different national contexts and how we can scale-up their impact or share lessons across European cities. This project brings together leading European research partners and practitioners to investigate urban living labs and enhance their potential for contributing to sustainability transitions.