A megacity is an urban area with a population of over 10 million people. It typically consists of multiple cities or metropolitan areas that have grown together to form one large, densely populated region.
Related terms
Urbanization: The process of the population shifting from rural areas to urban areas.
Metropolitan Area: A region consisting of a central city and its surrounding suburbs and towns.
City Cluster: An agglomeration of several cities and towns located close to each other, often forming a continuous built-up area.