To achieve a transformation toward the circular economy, organizations need to take an ecosystem perspective and consider multiple complementary actors that are needed to deliver circularity as a collective outcome. However, practitioners and scholars lack an understanding of the initial phases of ecosystem creation, in terms of how to get started, and what to consider. We therefore investigate how organizations can initiate an ecosystem for a circular economy. The method consists of a concise review of the ecosystem literature and three instrumental cases, to identify important activities that are needed when initiating an ecosystem for circularity. The cases include: (1) an alliance for circular safety footwear, (2) a startup that turns old coffee ground and orange peel waste from another company into new products, and (3) a multi-stakeholder project aimed at recovering resources from wastewater. We propose a framework for a Minimum Viable Ecosystem for Circularity (MVEC) that includes a set of key activities to perform when building ecosystems for a circular economy. These activities provide a useful roadmap for scholars and practitioners for establishing and assessing ecosystems for circularity. We call for further research and practical applications to test and demonstrate the utility of this framework in different contexts.