This document is a guidebook for building regional networks for urban sustainability. It provides lessons learned from existing regional networks supported by the Urban Sustainability Directors Network. The guidebook contains advice on starting a regional network, including identifying common challenges faced in the early stages. It explains that regional networks allow local government sustainability leaders to share knowledge and best practices across cities. Several examples are given of sustainability directors who successfully started regional networks in order to collaborate more closely on sustainability initiatives within their states or regions. The guidebook aims to help new network developers by outlining practical strategies and processes based on the experiences of existing networks.