The United Nations describes a megacity as an urban center that accommodates more than 10 million inhabitants.
The megacities in this list, also face "mega" challenges, including providing water services and managing their environment; however, urbanization does not mean a threat to the natural environment.
'Well-planned, compact urban development generates immense environmental value', according to the U.N.'s World Cities Report 2020
The cities listed below are the most populous in the world, according a 2018 U.N. report.
1. Tokyo, Japan
Population in Urban Area: 37,340,000
Population in City Area: 13.96 m
Tokyo is the most populated city in the world and the largest "Megacity" in the world.
The city dubbed the "Capital of the East" is located on the eastern coast of the Japanese main island of Honshu.
2. Delhi, India
Population in Urban Area: 31,181,000
Population in City Area: 20,591,874
Delhi, also known as the National Capital Territory of India is the largest city in the country. According to a U.N. report, the Indian capital is expected to retain the spot of the world's second most populous city through at least 2030.
3. Shanghai, China
Population in Urban Area: 27,796,000
Population in City Area: 22,315,474
This is China's most populated and also wealthiest city. Situated in the Yangtze River Delta, in eastern China, it has a huge business district, two large airports (Pudong and Hongqiao) and the world's fastest train (the Shanghai Maglev).
4. São Paulo, Brazil
Population in Urban Area: 22,043,028
Population in City Area: 10,021,295
This bustling metropolis in southeast Brazil, is the largest city of the Southern Hemisphere and the largest Portuguese-speaking city in the world.
5. Mexico City, Mexico
Population in Urban Area: 21,919,000
Population in City Area:12,294,193
Greater Mexico City refers to Mexico City and the 60 adjacent municipalities of the states of Mexico and Hidalgo
The oldest capital city in the Americas, it is is the largest Spanish-speaking city in the world.
6. Cairo, Egypt
Population in Urban Area: 21,323,000
Population in City Area: 8.1 m
Cairo is the largest city in Africa and the Middle East.
7. Mumbai, India
Population in Urban Area: 20,668,000
Population in City Area:12,691,836
Mumbai, which was official named Bombay until 1995, is the capital of the State of Maharashtra.
The city is India's financial and commercial centre, and the country's principal port on the Arabian Sea. Like other industrial megacities, it suffers with air and water pollution, as well as overcrowding.
8. Beijing, China
Population in Urban Area: 20,897,000
Population in City Area: 11,716,620
About 21 million people live in Beijing, the capital of China, which makes it the world's most populous capital city.
9. Dhaka, Bangladesh
Population in Urban Area: 21,741,000
Population in City Area: 10,356,500
Located on the banks of the Buriganga River, Dhaka is the capital and the biggest city of Bangladesh.
The city is the most densely populated on Earth, with nearly 37 people living in every square kilometer. The Greater Dhaka Area has a total population of more than 21 million.
Dhaka is also considered the rickshaw capital of the world, with the carts being the most popular method of transportation.
10. Osaka, Japan
Population in Urban Area:19,111,000
Population in City Area: 2,592,413
Japan's second largest city joins Tokyo on the list.
It is located in the Kansai region of the main island of Honshū, at the mouth of the Yodo River on Osaka Bay, relatively near to the ancient Japanese capital, Kyoto.
The port city is particularly known for its modern architecture and its street bars. Osaka is also home to the country's first Buddhist temple, Shi Tenno-ji.
11. New York, U.S.
Population in Urban Area: 18,823,000
Population in City Area:8.3 m
The first megacity in human history, New York is the most populous city in the United States. It also has the highest population density in the country, with over 10,194 people for every square kilometer.
According to Population Stat ,which uses sources from World Bank and United Nations, Census,New York City "is predicted to more than double in size by 2035, up to 20.8 million residents in the New York City urban area."
12. Karachi, Pakistan
Population in Urban Area: 16,459,000
Population in City Area: 11,624,219
Pakistan economic and financial capital on the Arabian Sea. Karachi is the country's largest city and a major seaport, serving among others the landlocked country of Afghanistan.
A World Bank report from 2018, "Transforming Karachi into a Livable and Competitive Megacity," says that despite being a large city that is home to many, "Karachi has seen a substantial decline in quality of life and economic competitiveness in recent decades.
"Basic service delivery is very poor, with very low indicators for water supply, sanitation, public transport and public spaces. Pollution levels are high, and the city is vulnerable to disasters and climate change."
13. Buenos Aires, Argentina
Population in Urban Area: 15,258,000
Population in City Area:3m
Buenos Aires has a population of almost 3 million, with a metropolitan population of over 15 million. The capital and largest city in Argentina, it is located on the western shore of the Rio de la Plata .
With over 400 theaters, Buenos Aires is sometimes called the 'World's Capital of Theater'.
14. Chongqing, China
Population in Urban Area: 16,382,000
Population in City Area: 7,457,600
A modern port city and a district in Central China, Chongqing is the largest municipality in southwest China with an area of 31,800 square miles (82,400 square kilometers).
15. Istanbul, Turkey
Population in Urban Area: 15,415,197
Population in City Area:14,804,116
Istanbul, Turkey's largest city extends between Europe and Asia across the Bosphorus Strait.
Nearly two thirds of its residents live on the European side of the city, and the rest live on the Anatolian side.
16. Kolkata, India
Population in Urban Area: 14,974,000
Population in City Area: 4,631,392
The capital and the largest city of the Indian state of West Bengal. Located on the banks of the Hooghly River, Kolkata is a city of commerce, transport, and manufacture, and the dominant urban centre of eastern India.
Formerly known as Calcutta, an Anglicized version of the Bengali name Kalikata.
17. Manila, Philippines
Population in Urban Area:14,159,000
Population in City Area:1,600,000
The capital of the Philippines, it is located on the island of Luzon and spreads along the eastern shore of Manila Bay. Manila faces problems with overcrowding which has resulted in housing shortage, congestion and air pollution.
18. Lagos, Nigeria
Population in Urban Area: 14,862,000
Population in City Area: 9 m
The second most populous city in Africa, its population continues to rise and according to Population Stat, "experts predict that by 2035, the city will have 24.4 million people and that by 2050, the population will double and make the city one of the top three largest in the entire world."
19. Rio de Janeiro, Brazil
Population in Urban Area: 13,544,000
Population in City Area: 6,023,699
The second-most populous city in Brazil, Rio de Janeiro City is home to over 6 million people, about 35 percent of the population of Rio de Janeiro State.
Rio has the second biggest municipal GDP of Brazil estimated at about $201 billion USD.
20. Tianjin, China
Population in Urban Area: 13,794,000
Population in City Area: 11,090,314
After Shanghai and Beijing, it is the third largest municipality of China. It is also the main port of Northern China , often called "the gate of Beijing," and the biggest port created by man in China. The port occupies an area of 107 km2 and a quay with a length of 21.5 km
21. Kinshasa, DR Congo
Population in Urban Area:14,970,000
Population in City Area: 7,785,965
Africa's third-largest metropolitan area after Cairo and Lagos, it is the world's largest Francophone urban area, French is the official language but Lingala, a Bantu language, is used as a lingua franca in the streets.
22. Guangzhou, China
Population in Urban Area: 13,635,397
Population in City Area:11,071,424
One of China's three largest cities.
A major port, it was "part of the Silk Route of the Sea" from the third century, during the reign of the Qin dynasty. The main part of the city is situated on the north bank of the Pearl River, about 120 km north-northwest of Hong Kong .
23. Los Angeles, U.S.
Population: 12,459,000
Population in City Area: 3.9 m
The Los Angeles metropolitan area is the second-largest metropolitan area in the nation after New York. Located near the Pacific coast in Southern California, most of the population of the Los Angeles metropolitan area is centralized in the City of Los Angeles.
24. Moscow, Russia
Population in Urban Area: 12,593,000
Population in City Area: 10,381,222
The capital of Russia and the northernmost major city in the world. Moscow, is the second most populated city in Europe, after Istanbul in Turkey.
The Moscow metro system is the third busiest in the world and shuttles up to 6-million people on a daily basis.
25. Shenzhen, China
Population in Urban Area: 12,592,000
Population in City Area: 10,358,381
Located next to Hong Kong, it is the home of the most high-rise buildings in China. Shenzhen wasn't technically a city until 1979 but only 42 years later, it is the largest economy in China's Greater Bay Area.
According to Statista, Shenzhen is "one of the fastest growing cities in China. Based on estimates, the population of Shenzhen is expected to reach over 15 million by 2035. This rapidly growing city is attracting an increasing number of young Chinese, who want to start and grow their careers."
The population estimates and projections come from the U.N, World Urbanization Prospects and Macrotrends data.
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