This thesis aimed to deepen understanding of the potential health benefits of urban greenspace, by identifying associations between different greenspace characteristics and mental wellbeing. A systematic literature review revealed that, while local area greenspace is adequately associated with life satisfaction, evidence for other characterisations of greenspace (type, accessibility, etc) is less sufficient. Although findings are currently not specific enough to guide planning decisions, there is a need to examine multidimensional wellbeing measures and greenspace in detail. A first study of local area greenspace and mental wellbeing in England, using data from 31,000 individuals in the UK Household Longitudinal Study survey and greenspace information (Generalised Land Use Database), found that Ordinary Least Squares associations between local prevalence of greenspace and multidimensional wellbeing could not be detected at census level, perhaps due to the imposition of arbitrary boundaries. More detailed post code-level data was obtained for 25,000 London residents completing the Annual Population Survey 2012-2015, with greenspace shapefiles from the Greenspace Information for Greater London group. The amount of greenspace within a 300m buffer of individuals homes was positively and significantly associated with hedonic and eudaimonic wellbeing. Geographically Weighted Regression models, addressing spatial clusters within the data, revealed slight variation in the strength of these associations across the study space. The final study, which characterised greenspace by type and accessibility on foot, found natural greenspace to be positively associated with hedonic wellbeing, but not eudaimonic wellbeing; associations with other types of greenspace were not significant. Spatial Error models allowed second-order processes within the structure of the data to be captured. These contributions are the first to examine nature planning recommendations for potential associations with mental wellbeing, expanding the current knowledge of greenspace design. Informed design should consider both the characteristics of the greenspace and local residents, to benefit the mental wellbeing of individuals and society as a whole.