In this paper, the authors conceptualize Open Data ecosystems by analysing the major stakeholders in the UK. The conceptualization is based on a review of popular Open Data definitions and business ecosystem theories, which are applied to qualitative empirical data. The work is informed by a combination of discourse analysis and a content analysis of in-depth interviews, undertaken during the summer of 2013. Drawing on the UK as a best practice example, the authors examine a set of structural business ecosystem properties: circular flow of resources, sustainability, demand that encourages supply, and dependence developing between suppliers, intermediaries, and users. The authors identify that gaps and shortcomings remain. Most prominently, demand is not yet fully encouraging supply and actors have yet to experience fully mutual interdependence.