Tokyo is the world's largest megacity
Gangnam-gu district of Seoul
Mumbai City

A megacity is usually defined as a metropolitan area with a total population in excess of 10 million people.[1] Some definitions also set a minimum level for population density (at least 2,000 persons/square km).[citation needed] A megacity can be a single metropolitan area or two or more metropolitan areas that converge. The terms conurbation, metropolis and metroplex are also applied to the latter. The terms "megapolis'" and megalopolis are sometimes used synonymously with megacity," though those terms denote a semi-continuous chain of large metropolitan cities.[citation needed]

As of 2011, there are 21 megacities in existence, which is the official figure despite the list below containing 27 megacities [2] – with conurbations such as Mumbai,[3] Tokyo, New York City, Dhaka, and Mexico City having populations in excess of 20 million inhabitants each. New Megacities like Johannesburg have population of over 10 million.



In 1800, only 3% of the world's population population lived in cities, a figure that has risen to 47% by the end of the twentieth century. In 1950, there were 83 cities with populations exceeding one million; by 2007, this number had risen to 468.[4] If the trend continues, the world's urban population will double every 38 years. The UN forecasts that today's urban population of 3.2 billion will rise to nearly 5 billion by 2030, when three out of five people will live in cities.[5]

This increase will be most dramatic on the least-urbanized continents, Asia and Africa. Surveys and projections indicate that all urban growth over the next 25 years will be in developing countries.[6] One billion people, almost one-seventh of the world's population, now live in shanty towns.[7] In many poor countries overpopulated slums exhibit high rates of disease due to unsanitary conditions, malnutrition, and lack of basic health care.[8] By 2030, over 2 billion people in the world will be living in slums.[9] Over 90% of the urban population of Ethiopia, Malawi and Uganda, three of the world's most rural countries, already live in slums.

By 2025, according to the Far Eastern Economic Review, Asia alone will have at least 10 megacities, including Mumbai, India (33 million), Shanghai, China (27 million), Karachi, Pakistan (26.5 million), Dhaka, Bangladesh (26 million) and Jakarta, Indonesia (24.9 million people).[10] Lagos, Nigeria has grown from 300,000 in 1950 to an estimated 12.5 million today, and the Nigerian government estimates that the city will have expanded to 25 million residents by 2015.[11]

Largest cities


For almost a thousand years, Rome was the largest, wealthiest, and most politically important city in Europe.[12] Its population passed a million people by the end of the 1st century BC.[13] Rome's population started dropping in 402 AD when Flavius Honorius moved the government to Ravenna and Rome's population declined to a mere 20,000 during the Early Middle Ages, reducing the sprawling city to groups of inhabited buildings interspersed among large areas of ruins and vegetation.

Baghdad was likely the largest city in the world from shortly after its foundation in 762 AD until the 930s, with some estimates putting its population at over one million.[14]

Chinese capital cities Chang'an, Kaifeng also experienced huge population booms during prosperous empires. According to the census in the year 742 recorded in the New Book of Tang, 362,921 families with 1,960,188 persons were counted in Jingzhao Fu (京兆府), the metropolitan area including small cities in the vicinity.[15]

São Paulo, Brazil
Manila, Philippines
Shanghai, China

The medieval settlement surrounding Angkor, the one-time capital of the Khmer Empire which flourished between the 9th and 15th centuries, could have supported a population of up to one million people.[16]

In 1950, New York City was the only urban area with a population of over 10 million.[17] Geographers had identified 25 such areas as of October 2005,[18] as compared with 19 megacities in 2004 and only nine in 1985. This increase has happened as the world's population moves towards the high (75–85%) urbanization levels of North America and Western Europe. The 1990 census marked the first time the majority of US citizens lived in cities with over 1 million inhabitants.

In the 2000s, the largest megacity is the Greater Tokyo Area. The population of this urban agglomeration includes areas such as Yokohama and Kawasaki, and is estimated to be between 35 and 36 million. This variation in estimates can be accounted for by different definitions of what the area encompasses. While the prefectures of Tokyo, Chiba, Kanagawa, and Saitama are commonly included in statistical information, the Japan Statistics Bureau only includes the area within 50 kilometers of the Tokyo Metropolitan Government Offices in Shinjuku, thus arriving at a smaller population estimate.[19][20] A characteristic issue of megacities is the difficulty in defining their outer limits and accurately estimating the populations.

Based on the population criteria, the world's 27 megacities are, in rank of population:

Rank Megacity Country Continent Population Annual Growth[citation needed]
1 Tokyo Japan Japan Asia 34,300,000 0.60%
2 Guangzhou China China Asia 25,200,000 4.00%
3 Seoul South Korea South Korea Asia 25,100,000 1.40%
4 Shanghai China China Asia 24,800,000 2.20%
5 Delhi India India Asia 23,300,000 4.60%
6 Mumbai India India Asia 23,000,000 2.90%
7 Mexico City Mexico Mexico North America 22,900,000 2.00%
8 New York City United States USA North America 22,000,000 0.30%
9 São Paulo Brazil Brazil South America 20,900,000 1.40%
10 Manila [21] Philippines Philippines Asia 20,300,000 2.50%
11 Jakarta Indonesia Indonesia Asia 18,900,000 2.00%
12 Los Angeles United States USA North America 18,100,000 1.10%
13 Karachi Pakistan Pakistan Asia 17,000,000 4.90%
14 Osaka Japan Japan Asia 16,700,000 0.15%
15 Kolkata India India Asia 16,600,000 2.00%
16 Cairo Egypt Egypt Africa 15,300,000 2.60%
17 Buenos Aires Argentina Argentina South America 14,800,000 1.00%
18 Moscow Russia Russia Europe 14,800,000 0.20%
19 Dhaka Bangladesh Bangladesh Asia 14,000,000 4.10%
20 Beijing China China Asia 13,900,000 2.70%
21 Tehran Iran Iran Asia 13,100,000 2.60%
22 Istanbul Turkey Turkey Europe & Asia 13,000,000 2.80%
23 London United Kingdom United Kingdom Europe 12,500,000 0.70%
24 Rio de Janeiro Brazil Brazil South America 12,500,000 1.00%
25 Lagos Nigeria Nigeria Africa 12,100,000 3.20%
26 Paris France France Europe 10,197,678 1.00%

Source: Th. Brinkhoff: The Principal Agglomerations of the World, 2011-07-01

Another list defines megacities as urban agglomerations instead of metropolitan areas.[22] As of 2010, there are 25 megacities by this definition.


Smog in Cairo, Egypt. Cairo is the sixteenth most populous city in the world.


According to the United Nations, the proportion of urban dwellers living in slums decreased from 47 percent to 37 percent in the developing world between 1990 and 2005.[23] However, due to rising population, the absolute number of slum dwellers is rising. The majority of these come from the fringes of urban margins, located in legal and illegal settlements with insufficient housing and sanitation. This has been caused by massive migration, both internal and transnational, into cities, which has caused growth rates of urban populations and spatial concentrations not seen before in history. These issues raise problems in the political, social, and economic arenas. Slum dwellers often have minimal or no access to education, healthcare, or the urban economy.


Megacities often have significant numbers of homeless people. The actual legal definition of homelessness varies from country to country, or among different entities or institutions in the same country or region.[24]

Traffic congestion

Traffic congestion is a condition on road networks that occurs as use increases, and is characterized by slower speeds, longer trip times, and increased vehicular queueing.

Urban sprawl

A flat land area in the greater Los Angeles area almost completely filled with houses, buildings, roads, and freeways. Areas constructed to capacity contribute to urban expansion.

Urban sprawl, also known as suburban sprawl, is a multifaceted concept, which includes the spreading outwards of a city and its suburbs to its outskirts to low-density, auto-dependent development on rural land, with associated design features that encourage car dependency.[25] As a result, some critics argue that sprawl has certain disadvantages, including, longer transport distances to work, high car dependence, inadequate facilities e.g.: health, cultural. etc. and higher per-person infrastructure costs. Discussions and debates about sprawl are often obfuscated by the ambiguity associated with the phrase. For example, some commentators measure sprawl only with the average number of residential units per acre in a given area. But others associate it with decentralization (spread of population without a well-defined center), discontinuity (leapfrog development), segregation of uses, etc.[citation needed]


Gentrification and urban gentrification denote the socio-cultural changes in an area resulting from wealthier people buying housing property in a less prosperous community.[26] Consequent to gentrification, the average income increases and average family size decreases in the community, which may result in the informal economic eviction of the lower-income residents, because of increased rents, house prices, and property taxes. This type of population change reduces industrial land use when it is redeveloped for commerce and housing. In addition, new businesses, catering to a more affluent base of consumers, tend to move into formerly blighted areas, further increasing the appeal to more affluent migrants and decreasing the accessibility to less wealthy natives.

Environmental problems

Air pollution

Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or damages the natural environment, into the atmosphere. Many urban areas have significant problems with smog, a type of air pollution derived from vehicular emission from internal combustion engines and industrial fumes that react in the atmosphere with sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog.

Smog is also caused by large amounts of coal burning, which creates a mixture of smoke and sulfur dioxide. World coal consumption was about 6,743,786,000 short tons in 2006[27] and is expected to increase 48% to 9.98 billion short tons by 2030.[28] China produced 2.38 billion tons in 2006. India produced about 447.3 million tons in 2006. 68.7% of China's electricity comes from coal. The USA consumes about 14% of the world total, using 90% of it for generation of electricity.[29]

In fiction

See also


  1. ^ "How Big Can Cities Get?" New Scientist Magazine, 17 June 2006, page 41.
  2. ^ "7 Billion, National Geographic Magazine". Accessed January 2011.
  3. ^ "Mumbai" - Type of Geographical entity. Accessed May 2010.
  4. ^ "Principal Agglomerations of the World". Retrieved 2010-09-01. 
  5. ^ "Megacities Of The Future". 2007-06-11. Retrieved 2010-09-01. 
  6. ^ "Nigeria: Lagos, the mega-city of slums". Retrieved 2010-09-01. 
  7. ^ Whitehouse, David (2005-05-19). "Half of humanity set to go urban". BBC News. Retrieved 2010-09-01. 
  8. ^ "Planet of Slums - The Third World’s Megacities". Retrieved 2010-09-01. 
  9. ^ "State of World Population 2007". Retrieved 2010-09-01. 
  10. ^ May 20, 2006 (2006-05-20). "Planet of Slums by Mike Davis". Retrieved 2010-09-01. 
  11. ^ "Lagos, Nigeria facts". National Geographic. 2006-07-28. Retrieved 2010-09-01. 
  12. ^ "Roman Empire Population". Retrieved 2010-09-01. 
  13. ^ "Population crises and cycles in history". Retrieved 2010-09-01. 
  14. ^ "Largest Cities Through History". 2010-06-16. Retrieved 2010-09-01. 
  15. ^ New Book of Tang, vol. 41 (Zhi vol. 27) Geography 1.
  16. ^ Metropolis: Angkor, the world's first mega-city, The Independent, August 15, 2007
  17. ^ Tertius Chandler, 1987, St. David's University Press. "Top 10 Cities of the Year 1950". Four Thousand Years of Urban Growth: An Historical Census. Retrieved 2007-03-24. 
  18. ^ "Population statistics". Retrieved 2010-09-01. 
  19. ^ "Greater Tokyo population statistics". 2008-10-01. Retrieved 2010-09-01. 
  20. ^ "Tokyo metropolitan area population statistics". Retrieved 2010-09-01. 
  21. ^ When counting the country's population, the population in the city extends to the whole Metropolitan Area although it is an entry as a city only
  22. ^
  23. ^ "p. 26" (PDF). Retrieved 2010-09-01. 
  24. ^ "Glossary defining homelessness". Retrieved 2010-09-01. 
  25. ^ What is Sprawl?. Retrieved on 2008-02-07.
  26. ^ Benjamin Grant (June 17, 2003). Urban gentrification is associated with movement "PBS Documentaries with a point of view: What is Gentrification?". Public Broadcasting Service. Urban gentrification is associated with movement. 
  27. ^ World coal consupmption 1980-2006 October 2008 EIA statistics
  28. ^ EIA, World Energy Projections Plus (2009)
  29. ^ "U.S. Coal Supply and Demand". Retrieved 2010-09-01. 
  30. ^ Sharp, Michael D. (2005). Popular Contemporary Writers. Marshall Cavendish. ISBN 0761476016. 
  31. ^ Namu, Adilifu (2008). Black space: imagining race in science fiction film. University of Texas Press. ISBN 0292717458. 
  32. ^ Westfahl, Gary (2005). The Greenwood encyclopedia of science fiction and fantasy: themes, works, and wonders, Volume 2. Greenwood Publishing Group. ISBN 0313329524. 


  • Soja, Edward W., "Postmetropolis, Critical Studies of Cities and Regions", Blackwell Publishing Ltd., 2000 (alk. paper, ISBN 1557180003; paperback, ISBN 1557180011)

External links

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Look at other dictionaries:

  • megacity — UK US (plural megacities) (also mega city, mega city) /ˈmeɡəˌsɪti/ noun [C] ► a very large city that has a population of more than 10 million people and that is often made of two or more urban areas that have grown so much that they are connected …   Financial and business terms

  • megacity — (n.) also mega city, 1968, from MEGA (Cf. mega ) + CITY (Cf. city) …   Etymology dictionary

  • Megacity — Tokio Als Megastadt werden im Allgemeinen Städte bezeichnet, die mehr als drei (beziehungsweise je nach Definition mehr als fünf, acht oder zehn) Millionen Einwohner haben. Ein oft alternativ genutzter Begriff ist „megaurbaner Raum“. Dieser… …   Deutsch Wikipedia

  • megacity — noun A very large city; a megalopolis. The largest megacity is the Greater Tokyo Area …   Wiktionary

  • megacity — /ˈmɛgəsɪti/ (say meguhsitee) noun a metropolitan area with a population in excess of 10 million people. Megacities are often formed when two or more metropolises grow together. In 1950 only there were only two megacities in the world – New York… …   Australian-English dictionary

  • megacity — ˌˌ noun Etymology: mega + city : megalopolis 1 * * * /meg euh sit ee/, n., pl. megacities. a city having a population of one million or more. [1965 70; MEGA + CITY] * * * megacity /megˈə sit i/ noun 1. A city of over a million inhabitants …   Useful english dictionary

  • megacity — noun Date: 1967 megalopolis 1 …   New Collegiate Dictionary

  • megacity — /meg euh sit ee/, n., pl. megacities. a city having a population of one million or more. [1965 70; MEGA + CITY] * * * …   Universalium

  • Megacity — Me|ga|ci|ty, die: Megastadt …   Universal-Lexikon

  • Megacity — ⇡ Megastadt …   Lexikon der Economics

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