Even small parks in the heart of our cities can protect us from strokes and heart disease, perhaps by cutting stress or boosting exercise.
Their study, in The Lancet, matched data about hundreds of thousands of deaths to green spaces in local areas.Councils should introduce more greenery to improve wellbeing, they said.
Across the country, there are "health inequalities" related to income and social deprivation, which generally reflect differences in lifestyle, diet, and, to some extent, access to medical care.
This means that in general, people living in poorer areas are more likely to be unhealthy, and die earlier.
However, the researchers found that living near parks, woodland or other open spaces helped reduce these inequalities, regardless of social class.
When the records of more than 366,000 people who died between 2001 and 2005 were analysed, it revealed that even tiny green spaces in the areas in which they lived made a big difference to their risk of fatal diseases.
Although the effect was greatest for those living surrounded by the most greenery, with the "health gap" roughly halved compared with those with the fewest green spaces around them, there was still a noticeable difference.