This French-language academic volume examines the world’s largest cities as major sites of metropolitan expansion and urban transformation. Framed through geography and urban studies, it considers how very large cities develop, how their spatial and social structures change, and how metropolitan areas function within wider national and global systems. The work is useful for readers interested in urbanization and regional development, particularly the relationship between demographic growth and economic concentration in contemporary cities. Rather than treating megacities as isolated cases, it places them in a comparative international perspective, highlighting recurring patterns and distinctive urban dynamics across different parts of the world.