Urbanization is a complex, multifaceted phenomenon and a defining feature of our times that is profoundly transforming our lives. The rapidly increasing concentration of the population in cities in the twenty-first century raises major issues in terms of sustainability. While it presents considerable challenges, it also offers opportunities to build more sustainable, fairer, and more resilient cities. This chapter will explore the subtleties of this dynamic, analyzing its causes, impacts, and the challenges it poses for building sustainable cities. It is imperative to implement long-term strategies, involving all actors in society: public authorities, businesses, and citizens. In this context, several factors contribute to the acceleration of urbanization, including rural–urban migration, population growth, technological progress, economic opportunities, and the impacts of urbanization on sustainability. This rapid urbanization has multiple consequences on the environment and society such as pressure on natural resources, pollution, climate change, and many others. In order to build sustainable cities and face these challenges, it is essential to develop cities that meet the needs of present generations without compromising those of future generations, by the transition to clean energy sources is essential to reduce greenhouse gas emissions via the development of renewable energies solar hydraulic and ionic, etc., also think about waste management especially in an intelligent way by the establishment of intelligent, selective and recycling collection systems to limit the impact of waste on the environment, and why not establish the protection of biodiversity and the preservation of green spaces and the creation of intelligent ecological corridors which is essential to maintain biodiversity in the city, in its modern sense, obviously intelligent cities benefiting from new technologies in the service of sustainability and in the context of intelligent urban governance.