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The 20 Largest Cities in the World

The world's population is growing. For United Nations World Population Day, we take a look at where.

Large crowd of people watching concert or sport eventInts Vikmanis/Shutterstock

What is the biggest city in the world?

Two thousand years ago, there were a mere 170 million people living on the entire planet Earth, according to The human race has been on an upward trajectory ever since—logging in at 7.7 billion people in 2019 and projected to reach 10 billion by the 22nd century. What the most populated cities in the world used to look like is equally shocking.

Our burgeoning population presents many challenges, according to the United Nations, especially as countries look to hit sustainability goals by 2030. Basically, the more humans there are on Earth, the more resources such as food, water, and the land we need, the more resources we take away from other species, and the more waste we generate.

There is some good news. Population increases are slowing down and in some countries, and elsewhere, some populations are shrinking, according to the U.N. Still, there are other places that are virtually bursting at the seams. For United Nations World Population Day, on July 11, we look at the 20 most populous metropolitan areas on the planet—defined as core cities plus their surrounding communities—as tallied by World Population Review.

GUANGDONG CHINAhumphery/shutterstock

20. Guangzhou, China

Current population: 12,967,862 million people

China is home to one of the most populated cities— Guangzhou. With an almost 3 percent rise in population since 2018, Guangzhou, the southern Chinese city at the head of the Pearl River Delta that was formerly known as Canton, is one of the biggest cities around. It's a commercial and trade hub—and has been since the 3rd century. Despite the physical expansion of the borders of the city over the decades and centuries, the vast majority of Guangzhou residents are packed into the city's nearby districts. People are also packing to move to the fastest growing cities in America.

Aerial view of Rio's Rocinha favela, on a sunny afternoon.mandritoiu/Shutterstock

19. Rio de Janeiro, Brazil

Current population: 13,374,275 million people

Almost 5,400 people per square kilometer are packed into this urban area on Brazil's coast. It's one of the most popular travel destinations in South America, and yet over 20 percent of its residents live in impoverished conditions in almost 800 favelas, or so-called "substandard" districts around town, according to The Rio Times. On the plus side, though, population growth is slowing, down from a high of 4.2 percent in 1965, to .61 percent in 2019. Although, it's still one of the most populated cities in the world. This is shocking considering how many people there are on earth


18. Tianjin, China

Current population: 13,396,402 million people

The population of this 12,000-square-kilometer port city in Northeastern China expanded by a whopping 188 percent between the years of 1953 and 1982. Luckily, growth has slowed considerably since then—it expanded a mere 1.3 percent between 2018 and 2019—but it's showing no signs of leveling off or even decreasing. Manufacturing is the largest industry in the city and accounts for its speedy and consistent growth. It's strange to think that there are major cities in the world with millions of residents, like Tianjin, but there are also tiny countries you never knew existed.

Manila, PhilippinesAl.geba/shutterstock

17. Manila, Philippines

Current population: 13,698,889 million people

Although growth in the urban population of Manila has actually slowed down over the years as the surrounding suburbs have seen an uptick in residents, that doesn't mean the city is getting any less crowded. In fact, it has the "highest density [for a] major municipality in the world," according to New Geography, averaging 14,500 people per square kilometer—with an astounding 70,000 per square kilometer in the city's densest district. That makes it one of the most populated cities in the world. Plus, with many poor migrants moving into Manila from rural areas, Manila's projected increasing growth rates are certain to put further strains on resources. Moving? These cities are most likely to deny you a mortgage.

BUSY NIGERIAN MARKET LAGOS, NIGERIAariyo olasunkanmi/shutterstock

16. Lagos, Nigeria

Current population: 13,903,620 million people

This port city—and the largest city in Africa—originated on the islands of the protected Lagos Lagoon, but has since expanded some 50-plus kilometers inland and now encompasses about 452 square kilometers. Its diverse population is represented by about 250 groups, many of which have emigrated both from the Nigerian countryside and from surrounding countries. The vast majority of residents—66 percent—live in slum conditions. The economic differences between countries across the globe also mean that one dollar will get you 50 different things around the world

KOLKATA, INDIARadiokafka/shutterstock

15. Kolkata, India

    Current population: 14,755,186 million people

    India (1.3 billion) and China (1.4 billion) are the two most populous countries in the world, so it should come as no surprise that Indian and Chinese cities rank as some of the most crowded. Kolkata, a.k.a. Calcutta, a former East Indian Company trading post, as well as the headquarters of Mother Teresa's Missionaries of Charity, is the third most inhabited metropolitan area in India—a trend that is slowing but, thanks to the increasing popularity of its suburbs, shows no signs of reversing any time soon. 

    ISTANBUL, TURKEYEvrenKalinbacak/shutterstock

    14. Istanbul, Turkey

    Current population: 14,967,667 million people

    Istanbul, formerly Constantinople, ranks as the most populated city in all of Europe, according to World Population Review (although technically, half of the city lies in Asia). This is a significant improvement of a sort, considering that it was the most populated city in the world back in 1502. Nevertheless, the city's residents doubled their population in the 1980s, when the parameters of its borders greatly expanded. It boasts the largest airport in the world—a lucky happenstance for one of the fastest-growing metropolises.

    Buenos Aires, ArgentinaSC Image/shutterstock

    13. Buenos Aires, Argentia

    Current population: 15,057,273 million people

    Although the capital city of Argentina has only 3 million people living within its urban core, its wider, 2,681-square-kilometer region is home to the second largest population in South America. Although the suburbs of the greater metropolitan region have burgeoned over the last 70 years, the city center has remained pretty constant, size-wise; its stagnant economy has meant that folks are more prone to move out of town than into it. The best cities that people move to usually have a strong economy, but the people living there actually define a city. People in cities across the world should think about how this is the kindest city in America.

    CHONGQING, CHINAasiastock/shutterstock

    12. Chongqing, China

    Current population: 15,354,067 million people

    Like many other cities in Asia, Chongqing has seen a big population spike—a hefty 3.5 percent since 2018. In fact, Chongqing is one of the fastest-growing cities in the world and, as World Population Review points out, that's not fixing to change anytime soon. The city has another problem in addition to its rapid expansion: Its workforce is shrinking while its population ages—an odd and sobering fact to consider in conjunction with the total population of the Chongqing municipality, which currently stands at a staggering 33 million people. By contrast, these are the smallest towns in America by population.

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