Megacity

A megacity is a very large city, typically with a population of more than 10 million people. The United Nations Department of Economic and Social Affairs (UN DESA) in its "World Urbanization Prospects" report defines megacities as urban agglomerations with over 10 million inhabitants. Reports from academics, the European Council, the Organisation for Economic Co-operation and Development delineate them as the metropolitan areas that are inhabited by more than a total population of 10 million people. The fast growth of the former is attributed to the proliferation of the latter. Infrequently in some sources, from five to eight million is considered the minimum threshold, along with a population density of at least 2,000 per square kilometre. The terms conurbation, metropolis, and metroplex are also applied to the latter.

The total number of megacities in the world varies between different sources and their publication dates. The world had 32 according to EU Global Human Settlement Layer (2024), 33 according to UN DESA (2025), 39 according to the OECD (2020), and 42 according to Demographia (2025). In total, at most 46 unique places are mentioned as megacities across these selected sources, although some of these are just agglomerated differently between them. A good percentage of these urban agglomerations are in the Global South's most populous countries – China and India. The other three-to-five countries with more than one megacity are Brazil, Indonesia, Japan, Pakistan, and the United States. African megacities are present in Angola, Democratic Republic of the Congo, Egypt, Nigeria and South Africa; European megacities are present in France, Germany, Russia, the United Kingdom, and Turkey (also in Asia); megacities can be found in Latin America in the countries of Brazil, Mexico, Colombia, Peru, and Argentina.

Many recent satellite image-based sources identify China's Pearl River Delta (anchored by Guangzhou) as the largest megacity and continuously built-up area of the world. However, as of 2025, the UN sees both urban centres of Guangzhou and Shenzhen in the Pearl River Delta as disjointed megacities, and instead lists Jakarta as the world's largest megacity. Older sources, such as OECD in 2020, still list Tokyo as the largest.

List of megacities Numbers in red with an asterisk (*) do not meet the 10 million threshold to be considered a megacity.

Megacity Image Country RegionEstimated populationUN DESA(2025) Demographia (2025)GHSL(2024) OECD(2020) Bangalore South Asia13,187,000 16,216,000 15,178,533 14,253,019 Bangkok Southeast Asia18,180,000 20,284,000 19,048,032 18,601,400 Beijing East Asia17,013,000 22,363,000 18,150,576 20,738,738 Bogotá South America10,624,000 10,734,000 10,419,361 10,544,590 Buenos Aires South America14,018,000 15,933,000 14,179,912 14,590,526 Cairo 25,566,000 22,684,000 25,230,325 27,925,433 Chaoshan East Asia* 12,187,00010,579,30313,891,202 Chennai South Asia11,153,000 11,950,000 11,466,400 11,528,915 Chongqing East Asia* 11,524,000 * * Delhi South Asia30,222,000 33,224,000 31,422,508 33,495,554 Dhaka South Asia36,585,000 25,305,000 37,307,160 22,762,988 Guangzhou East Asia27,563,000 69,562,000 42,987,704 16,650,322 Hangzhou East Asia* 12,422,000 * * Ho Chi Minh City Southeast Asia14,053,000 16,024,000 14,557,830 14,247,593 Hyderabad South Asia* 10,101,000 * * Istanbul EuropeWest Asia15,015,000 14,749,000 14,210,222 14,693,269 Jakarta Southeast Asia41,914,000 36,877,000 40,545,126 32,513,588 Johannesburg * 15,026,000 * * Karachi South Asia21,423,000 21,258,000 21,031,703 18,916,709 Kinshasa 10,944,000 13,060,000 12,945,683 10,077,694 Kolkata South Asia22,550,000 20,327,000 23,314,585 24,106,859 Lagos 12,792,000 15,283,000 12,486,045 12,642,198 Lahore South Asia15,156,000 14,256,000 14,305,060 15,696,939 Lima South America10,580,000 10,914,000 10,828,104 10,496,389 London Europe10,416,000 11,360,000 10,408,333 13,475,297 Los Angeles North America12,740,000 15,582,000 13,474,333 16,206,529 Luanda 11,370,000 11,892,000 11,672,134 10,212,263 Metro Manila Southeast Asia24,735,000 25,521,000 25,921,189 27,327,889 Mexico City North America17,734,000 18,942,000 17,639,164 19,229,491 Moscow Europe14,525,000 18,509,000 14,384,082 17,217,606 Mumbai South Asia20,203,000 26,237,000 20,453,270 23,435,141 New York City North America13,920,000 20,892,000 14,197,659 20,106,617 Osaka East Asia12,964,000 14,998,000 12,653,994 16,866,788 Paris Europe* 11,282,000 * 11,249,025 Rio de Janeiro South America* 12,546,000 * 11,068,999 São Paulo South America18,950,000 21,747,000 19,485,158 21,671,857 Seoul East Asia22,490,000 23,825,000 22,261,692 25,199,125 Shanghai East Asia29,559,000 45,115,000 30,678,616 30,504,083 Shenzhen East Asia13,878,000 Surabaya Southeast Asia* * * 10,695,358 Suzhou East Asia* 11,540,430 13,458,006 Taipei East Asia* * * 10,048,037 Tehran West Asia* 14,137,000 * 13,563,316 Tianjin East Asia* 12,095,000 * * Tokyo East Asia33,413,000 37,325,000 33,155,907 36,697,549 Wuhan East Asia* 10,041,000 * * Notes

History Pre-industrial era

In the Antiquity era, for almost five hundred years, Rome was the largest, wealthiest, and most politically important city of the ancient world, ruling over Europe, Western Asia and Northern Africa. Population estimates of 750,000–1,000,000 people by the end of the 1st century BC are generally given by scholars; however, that would require population densities as high as 72,150 per square kilometre. If densities were similar to those in the well-preserved cities of Pompeii and Ostia, the population would be around 500,000. 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. 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 (), the metropolitan area including small cities in the vicinity of Chang'an.New Book of Tang, vol. 41 (Zhi vol. 27) Geography 1. 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.

Formation of megacities

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. The term "megacity" entered common use in the late 19th or early 20th centuries; one of the earliest documented uses of the term was by the University of Texas in 1904. Initially, the United Nations used the term to describe cities of 8 million or more inhabitants, but now uses the threshold of 10 million. In the mid-1970s, the term was coined by urbanist Janice Perlman referring to the phenomenon of very large urban agglomerations.

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. Cited in 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.

A characteristic issue of megacities is the difficulty in defining their outer limits and accurately estimating the populations. To correct for this an Urban Metric System was proposed, including measurement of Paropolis, that has tantamount calculation values to megacities. It has been applied limitedly, for example by Canada in cases since 2018. Another list defines megacities as urban agglomerations instead of metropolitan areas.

Growth

Among the 27 megacities with populations over 10 million globally in 2007, 15 were situated in Asia. The top eight provincial capital cities in China with urban areas exceeding 400 km—Beijing, Shanghai, Tianjin, Guangzhou, Chongqing, Hangzhou, Wuhan, and Xi'an—accounted for 54.8% of the total urban area of all provincial capital cities in the country in 2015. Other sources list Nagoya the Rhine-Ruhr metropolitan region as megacities.

In 2010, UN forecasted that urban population of 3.2 billion would rise to nearly 5 billion by 2030, when three out of five, or 60%, of people would live in cities. This increase will be most dramatic on the least-urbanized continents, Asia and Africa. By 2025, Asia's growth alone modeled having at least 30 megacities.

Surveys and projections indicate that all urban growth over the next 25 years will be in developing countries. One billion people, almost one-seventh of the world's population, now live in shanty towns. In many poor countries, overcrowded slums exhibit high rates of disease due to unsanitary conditions, malnutrition, and lack of basic health care. By 2030, over 2 billion people in the world will be living in slums. Over 90% of the urban population of Ethiopia, Malawi and Uganda, three of the world's most rural countries, already live in slums.

Since 2025, Jakarta has surpassed Tokyo to be the largest megacity in the world.

Challenges

Slums

According to the United Nations, the proportion of urban dwellers living in slums or informal settlements decreased from 47 percent to 37 percent in the developing world between 1990 and 2005. However, due to rising population, the absolute number of slum dwellers is rising and passed 1 billion in 2018. The increase in informal settlement population 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. The majority of these are located in informal settlements which often lack sufficient quality housing, sanitation, drainage, water access, and officially recognized addresses. These issues raise problems in the political, social, and economic arenas. People who live in slums or informal settlements often have minimal or no access to education, healthcare, or the urban economy.

Crime

As with any large concentration of people, there is usually crime. High population densities often result in higher crime rates, as visibly seen in growing megacities such as Karachi, Delhi, Cairo, Rio de Janeiro, and Lagos.

Homelessness

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.

In 2002, research showed that children and families were the largest growing segment of the homeless population in the United States,FACS, "Homeless Children, Poverty, Faith and Community: Understanding and Reporting the Local Story", March 26, 2002