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A megacity is usually defined as a metropolitan area with a total population in excess of ten million people.[1] 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.

As of 2016, there are 35 megacities in existence, Chennai being the latest. The largest of these are the metropolitan areas of Tokyo and Jakarta, each of these having a population of over 30 million inhabitants. Tokyo is the largest metropolitan area, while Shanghai is the largest city proper.

Largest cities

This is the list as of 2015.

Rank Megacity Image Country Continent Population
1 Tokyo-Yokohama Tokyo Tower view.jpg Japan Asia 37,900,000
2 Jakarta Jakarta Skyline (Resize).jpg Indonesia Asia 30,000,000[2]
3 Seoul Seoul-Cityscape-03.jpg South Korea Asia 26,100,000
4 Delhi Smog in the skies of Delhi, India.jpg India Asia 25,703,000[3]
5 Shanghai Night view from the Bund.jpg China Asia 25,400,000
6 Karachi 120px Pakistan Asia 24,000,000[4]
7 New York City New York City skyline 09.jpg United States North America 23,632,722[5]
8 Mexico City Ciudad.Mexico.City.Distrito.Federal.DF.Reforma.Skyline.jpg Mexico North America 22,200,000
9 Beijing Beijing skyline at night.JPG China Asia 21,650,000
10 São Paulo Ponte e rio.jpg Brazil South America 21,250,000
11 Lagos Lagos Island.jpg Nigeria Africa 21,000,534[6]
12 Mumbai Mumbai night skyline.jpg India Asia 20,741,000[3]
13 Osaka Skyline in Osaka.JPG Japan Asia 20,260,000
14 Manila Bonifacio Global City.jpg Philippines Asia 20,040,000
15 Cairo Cairo by night.jpg Egypt Africa 18,810,000
16 Los Angeles Los Angeles Skyline at Night.jpg United States North America 18,550,288[7]
17 Dhaka Dhaka Skyline at Night.jpg Bangladesh Asia 18,250,000
18 Moscow Moscow-City skyline.jpg Russia Europe 16,900,000
19 Buenos Aires Aerial view - Palermo, Buenos Aires.jpg Argentina South America 16,500,000
20 Bangkok Bangkok - City skyline at mid day.JPG Thailand Asia 15,350,000
21 Istanbul Istanbul skyline at night - Kopya.jpg Turkey Europe/Asia 14,800,000
22 Kolkata Kolkata Skyline.jpg India Asia 14,766,000[3]
23 Rio de Janeiro Corcovado do Pão de Açúcar.jpg Brazil South America 14,450,000
24 London London skyline showing planned Bishopsgate Tower.jpg[citation needed] United Kingdom Europe 14,031,830[8]
25 Tehran Tehran Skyline.jpg Iran Asia 13,700,000
26 Guangzhou Guangzhou skyline.jpg China Asia 12,700,000
27 Kinshasa 2010-03-07-Kinshasa depuis Brazzaville.jpg Democratic Republic of Congo Africa 12,500,000
28 Shenzhen Shenzhen, with Eiffel tower in the backgrund.jpg China Asia 12,250,000
29 Paris Paris skyline from the observation deck of the Montparnasse tower, July 2015.jpg France Europe 12,005,077[8]
30 Rhine-Ruhr Düsseldorf skyline.JPG
Düsseldorf skyline shown
Germany Europe 11,316,429[9]


The term "megacity" entered common use in the late 19th or early 20th centuries, one of the earliest documented uses being by the University of Texas in 1904.[10] Initially the United Nations used the term to describe cities of 8 million or more inhabitants, but now uses the threshold of 10 million.[11]

In 1800, only 3% of the world's population lived in cities, a figure that rose 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.[12] 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.[13] 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.[14] One billion people, almost one-seventh of the world's population, now live in shanty towns.[15] In many poor countries overpopulated slums exhibit high rates of disease due to unsanitary conditions, malnutrition, and lack of basic health care.[16] By 2030, over 2 billion people in the world will be living in slums.[17] 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, Asia alone will have at least 28 megacities, including Mumbai, India (31.7 million people), Shanghai, China (31.4 million people), Delhi, India (35.6 million people), Tokyo, Japan (38.9 million people) and Seoul, South Korea (31.2 million people). Lagos, Nigeria has grown from 300,000 in 1950 to an estimated 15.2 million today.


For almost five hundred years, Rome was the largest, wealthiest, and most politically important city in Europe.[18] Its population passed one million people by the end of the 1st century BC.[19] Rome's population started declining in 402 AD when Flavius Honorius, Western Roman Emperor from 395 to 423, 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.[20] Chinese capital cities Chang'an and 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 of Chang'an.[21] 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.[22]

From around 1825 to 1918 London was the largest city in the world, with the population growing rapidly, it was the first city to reach a population of over 5 million in 1900. In 1950, New York City was the only urban area with a population of over 10 million.[23] Geographers had identified 25 such areas as of October 2005,[24] 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.

Since the 2000s, the largest megacity has been the Greater Tokyo Area. The population of this urban agglomeration includes areas such as Yokohama and Kawasaki, and is estimated to be between 37 and 38 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.[25][26] A characteristic issue of megacities is the difficulty in defining their outer limits and accurately estimating the populations.

Another list defines megacities as urban agglomerations instead of metropolitan areas.[27] As of 2010, there are 25 megacities by this definition, like Tokyo.[citation needed][needs update] Other sources list Nagoya[28] and the Rhein-Ruhr[29] as megacities.



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.[30] 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.[citation needed] These issues raise problems in the political, social, and economic arenas.[citation needed] Slum dwellers often have minimal or no access to education, healthcare, or the urban economy.

Crime and terrorism

The lack of proper and sufficient infrastructure and public services (such as proper sanitation, housing, education and healthcare) to support the growing population not only leads to the growth of slums, but also breeds discontent among urban dwellers, leading to high crime rates, as visibly seen in growing megacities such as Karachi, Rio de Janeiro and Lagos.[31]


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.[32]

In 2002, research showed that children and families were the largest growing segment of the homeless population in the United States,[33][34] and this has presented new challenges, especially in services, to agencies. In the USA, the government asked many major cities to come up with a ten-year plan to end homelessness. One of the results of this was a "Housing first" solution, rather than to have a homeless person remain in an emergency homeless shelter it was thought to be better to quickly get the person permanent housing of some sort and the necessary support services to sustain a new home. But there are many complications with this kind of program and these must be dealt with to make such an initiative work successfully in the middle to long term.[35][36]

Traffic congestion

Bangkok is notorious for its traffic congestion.

Traffic congestion is a condition on road networks that occurs as use increases, and is characterized by slower speeds, longer trip times, increased pollution, and increased vehicular queueing. The Texas Transportation Institute estimated that, in 2000, the 75 largest metropolitan areas experienced 3.6 billion vehicle-hours of delay, resulting in 5.7 billion U.S. gallons (21.6 billion liters) in wasted fuel and $67.5 billion in lost productivity, or about 0.7% of the nation's GDP. It also estimated that the annual cost of congestion for each driver was approximately $1,000 in very large cities and $200 in small cities.[citation needed] Traffic congestion is increasing in major cities and delays are becoming more frequent in smaller cities and rural areas.

Urban sprawl

A flat land area in the Greater Los Angeles Area in the U.S. state of California 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.[37] 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.[38] 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.

Air pollution

Air pollution is the introduction into the atmosphere of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or damages the natural environment. Many urban areas have significant problems with smog, a type of air pollution derived from vehicle emissions 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[39] and is expected to increase 48% to 9.98 billion short tons by 2030.[40] 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.[41]

Energy and Material Resources

The sheer size and complexity of megacities gives rise to enormous social and environmental challenges. Whether megacities can develop sustainably depends to a large extent on how they obtain, share, and manage their energy and material resources. There are correlations between electricity consumption, heating and industrial fuel use, ground transportation energy use, water consumption, waste generation, and steel production in terms of level of consumption and how efficiently they use resources.[42]

In fiction

Megacities are a common backdrop in dystopian science fiction, with examples such as the Sprawl in William Gibson's Neuromancer,[43] and Mega-City One, a megalopolis of between 50 and 800 million people (fluctuations due to war and disaster) across the east coast of the United States, in the Judge Dredd comic.[44] In Demolition Man a megacity called "San Angeles" was formed from the joining of Los Angeles, Santa Barbara, San Diego and the surrounding metropolitan regions following a massive earthquake in 2010.[45] Fictional planet-wide megacities (ecumenopoleis) include Trantor in Isaac Asimov's Foundation series of books and Coruscant (population 1 trillion) in the Star Wars universe.[46]

See also


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