It has been predicted that, by 2050, 70 per cent of the world’s population will be living in urban settlements. It is no wonder that the United Nations has taken note and is acknowledging cities now more than ever in global frameworks. Efforts to achieve global goals that improve the well-being and quality of life of citizens must now recognize their increasingly urban dimensions, a shift that culminated in the development of Sustainable Development Goal 11, to make cities and human settlements inclusive, safe, resilient and sustainable. This chapter explores the history of the development of SDG 11 and how this evolved from the narrow focus on cities in the Millennium Development Goals. It also analyses the growing role of city governments as transnational actors, working through an ecosystem of city networks to play a significant part in global environmental governance.