Europe is facing a number of global challenges such as digitalisation, migration, and climate change which increase demands on citizens’ resilience and puts them at risk of developing mental health problems. RECONNECTED responds to this problem by developing and testing a digital support system to promote resilience and connect vulnerable citizens in socially disadvantaged communities and evaluate whether this results in citizens’ improved mental health, increased mental health awareness, reduced stigma, and improved social participation, at affordable costs for implementation. Taking a complex systems approach, the project will first extend and test a recently developed theoretical integrative framework of urban mental health to include mental health responses to global transitions. This will provide a good understanding of how risk and protective factors at the individual, social, environmental, and societal levels interact dynamically and impact on mental health. The framework will provide actionable insights for policy decision making and will be used to develop a support system with intervention tools targeting individual and social levels simultaneously. The platform will be co-created with stakeholders in the local community in nine European countries. These interventions will be non-stigmatising and empowering and tailored to the needs of the local community. RECONNECTED will test the feasibility and effectiveness of the support system in these communities and, in the final stage, develop implementation scenarios that balance effectiveness with efficiency and scalability to inform policy decision making that can be used throughout Europe. The methodological approach in the project is theory-informed and data-driven, and we will use co-creation throughout the project to ensure that actionable insights and intervention tools are relevant, acceptable, and ethical to end-users and other stakeholders.