Enabling a shift towards a Circular Economy (CE) relies on the alliance of existing and new stakeholders, their innovations and capabilities, and new ways of working together to achieve a new system-level goal. This paper scrutinizes the emergence of CE ecosystems with a particular focus on two frontrunner actors: one large industrial manufacturer and one municipality within the same geographical region, both with the same ambition to drive a CE transition. Specifically, it investigates what CE ecosystems are emerging, each actor's role in these, and their untapped circularity potential. Based on interviews with respondents from each actor, the study contributes to the emerging literature on how CE ecosystems arise and develop. Furthermore, the paper discusses how the actors could seize missed potential opportunities for circular ecosystems in the region studied.