megacities

Megacities are urban areas with a population of 10 million or more in the surrounding metropolitan or urban agglomeration. The term is used to describe large, highly developed urban regions, but definitions vary depending on whether counting city proper, metropolitan area, or urban agglomeration. The United Nations and other statistical agencies monitor megacities as part of global urbanization trends.

Megacities are characterized by high population density, rapid growth, and a concentration of economic activity, services, and cultural institutions. They place substantial demands on housing, transportation, water, energy, and sanitation, while also driving innovation, trade, and job creation. Their scale makes governance complex, often requiring cross-jurisdiction coordination across multiple municipalities and sometimes overlapping planning authorities.

As of the early 2020s, Asia hosts the largest share of megacities, with growing representation in Africa and Latin America. Notable examples include Tokyo, Delhi, Shanghai, Mumbai, Dhaka, Lagos, Sao Paulo, and Mexico City. The total number of megacities is often cited around 33, though estimates vary with measurement method and data quality.

Planning responses emphasize metropolitan or regional approaches, investments in mass transit, affordable housing, and climate-resilient infrastructure. Challenges include informal settlements, congestion, air and water pollution, uneven service provision, and economic inequality, as well as vulnerabilities to climate change and natural disasters.

See also: urban agglomeration, megacity governance, urbanization.