The REFLOW Handbook is a practical resource designed to assist cities in their transition to circular and regenerative cities. This Handbook is open, iterative and participatory. The Handbook contextualises REFLOW and offers an initial investigation into the element of urban governance innovation, particularly with respect to the circular economy. Specifically, this document builds on exploratory research aimed at ‘collaborative governance design’, which will be further explored and expanded on within the REFLOW pilot cities. The Handbook concludes with an initial series of tested tools meant to assist cities in navigating the first steps of the transition.