The urgent challenge of achieving net zero carbon emissions by 2050 at the latest presents an opportunity to drive transformative changes in all sectors of society. Well designed actions to cut greenhouse gas (GHG) emissions could bring major benefits for health, by both reducing the health risks of climate change and delivering multiple benefits to human health and development (co-benefits). Modelling studies estimate that many millions of premature deaths could be prevented and GHG emissions greatly reduced by phasing out fossil fuels, thereby reducing air pollution, and by encouraging active travel, increasing use of public transport, and shifting to sustainable and healthy diets. Further benefits could accrue from efficient, well ventilated housing and from efforts to develop net zero health-care systems. There is also great potential to achieve health and climate benefits from nature-based solutions, including green space in cities, reforestation, and reduced deforestation and agroforestry. However, these potential benefits will only be realised by addressing key barriers and challenges.