Biodiversity and healthy natural ecosystems, including protected areas in and around cities, provide ecosystem benefits and services that support human health, including reducing flood risk, filtering air pollutants, and providing a reliable supply of clean drinking water. These services help to reduce the incidence of infectious diseases and respiratory disorders, and assist with adaptation to climate change. Access to nature offers many other direct health benefits, including opportunities for physical activity, reduction of developmental disorders and improved mental health. Economic valuations of green spaces in several cities globally have found that nature provides billions of dollars in cost savings for health services. Protected areas are increasingly common in, and around, cities to protect biodiversity and ecosystem services, including these benefits for health. Many cities are also launching programmes to enhance the health and environmental benefits of parks, based on a model of Healthy Parks, Healthy People, by Parks Victoria in Australia. Partnerships between conservationists, city planners and health authorities are critical to maximise these benefits. In some places, medical professionals prescribe time in nature, and some cities specify standards for urban green spaces to enhance their health benefits. The United Nations Sustainable Development Goals provide an important global framework for such partnerships from global to local level.