Despite clear signs that the impacts of climate change are escalating, the global response has been inadequate. Traditional scientific efforts have fallen short of providing knowledge and tools that have been broadly applied in decision-making, and innovative approaches to knowledge translation are needed. To catalyse climate action in Europe to protect public health, our overarching goal is to provide new knowledge, data, and tools on: i) the relationships between changes in environmental hazards caused by climate change, ecosystems, and human health; ii) the health co-benefits of climate action; iii) the role of health evidence in decision making; and iv) the societal implications of climate change for health systems. This will be achieved through five specific objectives: 1) to develop an integrated indicator framework and repository to track the status of health-relevant outcomes of climate actions; 2) to quantify the health co-benefits and full social and environmental costs and benefits resulting from mitigation measures outside of the health sector; 3) to develop innovative surveillance and forecasting tools that facilitate effective response to environmental health hazards (e.g. heat stress, allergenic pollen) caused by climate change and the design, monitoring and evaluation of interventions to mitigate climate change; 4) to investigate how stakeholders engage with evidence regarding the health impacts of climate change, and to develop strategies and tools to facilitate engagement; and 5) to provide evidence and training on the most effective strategies for climate change adaptation and mitigation for health systems, with specific focus on vulnerable populations including those occupationally exposed to hazards induced by climate change. CATALYSE is a powerful, interdisciplinary consortium with a mission to further develop and communicate evidence of the health impacts of climate change and respond to the urgent need for solutions. CATALYSE is part of the European cluster on climate change and health (name and acronym to be decided).