In 2014, over 54 per cent of the world's population were living in urban areas. The number will double to some 6.4 billion by 2050. Human mobility and migration play an important part in this trend. The report aims to consider migration as a defining factor alongside climate change, population growth, demographic change and economic crisis in shaping sustainable cities of the future. It examines both internal and international migration, at the city level and cities of the Global South. The report highlights the growing evidence of potential benefits of all forms of migration and mobility for city growth and development. It showcases innovative ways in which migration and urbanization policies can be better designed for the benefit of migrants and cities.