This City Region Food System (CRFS) toolkit provides guidance on how to assess and build sustainable city region food systems. It includes support material on how to: define and map your city region; collect data on your city region food system; gather and analyse information on different CRFS components and sustainability dimensions through both rapid and in-depth assessments; and how to use a multistakeholder process to engage policymakers and other stakeholders in the design of more sustainable and resilient city region food systems. The toolkit outlines the approach, techniques and tools used by seven cities that engaged in a CRFS assessment and planning process in the period 2015-2017. It tells the story of why and how they have been implementing this process and what outcomes they achieved. It is meant to be a resource for policymakers, researchers, and other key stakeholders and participants who want to better understand their own CRFS and plan for improvements.