The Circular Economy (CE) is heralded as an important concept with the potential to guide businesses and society toward a more sustainable future. However, while collaboration is widely accepted to play a central role in advancing circularity, little is known about how organizations effectively work together to achieve these outcomes. This is particularly problematic given that any shift toward collaboration requires systematic approaches based on effective collaborative processes between organizations. This conceptual paper addresses this gap by providing a comprehensive investigation of collaboration and circularity. The paper is based on a systematic literature review of 66 scientific publications as the foundation for analysis. Based on the analysis, the paper contributes to the CE literature by offering a novel approach to conceptualizing collaboration and circularity. A conceptual framework is provided which differentiates CE strategies at three stages of the product lifecycle. The paper makes a second contribution to the CE literature by examining the role that multilevel collaboration plays in facilitating a transition from a linear economy to a CE and, in particular, the significance of government in managing collaboration opportunities between partners. We highlight intermediaries as important accelerators in this transition. Future research directions are provided, including how government and intermediaries—among others—collaborate for CE transitions.