The Circular Economy (CE) is currently a popular notion within the policy and business advocacy groups. Despite being visionary and provocative in its message, the research on the CE concept is emerging. The two intertwined objectives of the talk are; first to identify, discuss and develop the various definitions provided by the emerging literature. Secondly, to suggest an initial research approach with which research on CE can be conducted. Our analysis shows that the existing CE work is mainly done on the practical and technical levels of the actual physical flows of materials and energy in production-consumption systems. The focus of the extant literature is on concrete metrics, tools, instruments and computations. Therefore, the basic assumptions concerning the values, societal structures, cultures, underlying world-views and the paradigmatic potential of CE remain largely unexplored. We argue that CE has already become what Gallie (1955) more than six decades ago termed as an “essentially contested concept”.