To support the world’s cities in reaping the benefits of urban and peri-urban forests, a few years ago Food And Agriculture Organisation, United Nations in 2016 initiated a collaborative process to develop voluntary guidelines aimed at optimizing the contributions of forests and trees to sustainable urban development. Scientists, practitioners and public administrators from cities worldwide were brought together in a series of workshops to discuss the elements and key challenges of urban forestry, and a smaller team of experts was assembled to distil this vast knowledge. This document is the ultimate result of that process. It is intended for a global audience, primarily comprising urban decision-makers, civil servants, policy advisors and other stakeholders to assist in developing urban and peri-urban forests as a way of meeting the present and future needs of cities for forest products and ecosystem services. The guidelines will also help increase community awareness of the contributions that trees and forests can make to improving quality of life, and of their essential role in global sustainability.