The prevention of childhood obesity is a global priority. However, a range of complex social and environmental influences is implicated in the development of obesity and chronic disease that goes beyond the notion of individual choice. A population-level approach recognises the importance of access to and availability of healthy foods outside the home. These external food environments, in restaurants, supermarkets, and in school, or recreation and sports settings, are often characterised by energy dense, nutrient-poor food items that do not reflect the current nutritional guidelines for health. In addition, our understanding of these broader influences on nutritional intake is still limited. Particularly, lacking is a clear understanding of what constitutes the food environment, as well as robust measures of components of the food environment across different contexts. Therefore, this review summarises the literature on food environments of relevance to childhood obesity prevention, with a focus on places where children live, learn and play. Specifically, the paper highlights the approaches and challenges related to defining and measuring the food environment, discusses the aspects of the food environment unique to children and reports on environmental characteristics that are being modified within community, school and recreational settings. Results of the review show the need for a continued focus on understanding the intersection between individual behaviour and external factors; improved instrument development, especially regarding validity and reliability; clearer reported methodology including protocols for instrument use and data management; and considering novel study design approaches that are targeted at measuring the relationship between the individual and their food environment.