Where tens of millions share a single metro
10 Largest Megacities in the World
Each of these urban regions is home to more people than most countries. Together they hold roughly one in fifteen humans on Earth.
A 'megacity' is usually defined as a metro area of more than 10 million people. Just a few decades ago the world had three. Today there are more than thirty, and the biggest of them now top thirty million.
How we chose these ↓ — jump to the full scoring system at the bottom of the article.
Seoul, South Korea · pop. 9,635,445
Roughly half of South Korea — about 26 million people — lives in the Seoul Capital Area, one of the most concentrated national populations on Earth. The metro region extends from Incheon's port and airport on the Yellow Sea through Seoul itself to satellite cities like Suwon and Seongnam.
The city has rebuilt itself completely since the Korean War, layering an aggressive 21st-century tech-and-K-pop economy onto a Joseon-era street grid. Its public transit system is among the world's best (see cities with the best public transit).
Osaka, Japan · pop. 2,691,185
The Keihanshin region around Osaka, Kyoto and Kobe holds roughly 19 million people, Japan's second megalopolis and still firmly in Tokyo's shadow but with its own distinct identity, accent and food culture (see best food cities).
Osaka was historically Japan's commercial capital and still hosts the headquarters of Panasonic, Sharp, Daikin and the country's pharmaceutical industry. The 2025 World Expo on Yumeshima island was the city's most prominent international moment in decades.
Beijing, China · pop. 21,893,095
Beijing's metropolitan region holds roughly 22 million people and is the political, cultural and intellectual counterweight to Shanghai's commerce. The city is the seat of every major Chinese government institution and home to most of the country's top universities.
The planned displacement of polluting industry, plus aggressive electric-vehicle adoption, has cut Beijing's notorious smog substantially since the mid-2010s. The 798 art district and the new Daxing International Airport, designed by Zaha Hadid, give a sense of the city's contemporary ambitions beyond Tiananmen and the Forbidden City.
Maharashtra, India · pop. 12,442,373
Squeezed onto a narrow peninsula jutting into the Arabian Sea, Mumbai's roughly 21 million residents share India's most expensive real estate and its busiest suburban rail system, which moves around 7 million passengers a day on the three Western, Central and Harbour lines.
The Bombay Stock Exchange and the Reserve Bank of India anchor the country's financial sector here, and Bollywood remains the largest film industry by output in the world. The contrast between the Dharavi informal settlement, one of the world's largest, and the high-rise wealth of Malabar Hill is the city's defining tension.
Mexico City, Mexico · pop. 9,209,944
The Valley of Mexico holds roughly 22 million people at 2,240 m elevation, easily the highest megacity on Earth (see highest-altitude cities). The basin was once a system of lakes drained by the Spanish; the modern city's persistent sinking, up to 40 cm a year in places, is the legacy of pumping the aquifer underneath.
The Aztec Templo Mayor sits a few metres below today's Zócalo, and excavations regularly turn up pre-Columbian artefacts whenever a new metro line goes through. Mexico City's air quality, once among the world's worst, has improved dramatically since the 1990s thanks to vehicle inspections and fuel reformulation.
Acre, Brazil
Greater São Paulo anchors the Western Hemisphere's largest metropolitan area, with roughly 22 million residents and a skyline of more apartment towers than any other city in the Americas. The Sé district at its centre captures the city's chaotic vertical density better than any photograph.
The city's economy alone is larger than that of most South American countries, and its food scene, increasingly recognised on the World's 50 Best, is the strongest argument for visiting beyond business. The Avenida Paulista on Sundays, closed to cars and packed with families, cyclists and buskers, is the single best snapshot of paulistano life.
Dhaka, Bangladesh · pop. 21,741,000
Dhaka is one of the densest cities on Earth — more than 23 million people packed into a delta footprint not much larger than Greater London. Population density in the historic core regularly exceeds 45,000 people per square kilometre, several times higher than Manhattan.
The city is the centre of Bangladesh's garment industry, which produces a meaningful share of the world's clothing exports. It is also one of the most sea-level-vulnerable megacities on Earth and features prominently on our list of cities most at risk from rising seas.
Shanghai, China · pop. 24,870,895
Shanghai's municipal area holds roughly 27 million people, with the larger Yangtze Delta megaregion home to over 100 million. The city is China's financial centre, the world's largest container port by throughput, and the eastern anchor of the country's high-speed rail network.
Pudong, the financial district east of the Huangpu, was farmland in 1990 and is now a forest of supertall skyscrapers including the Shanghai Tower, China's tallest building at 632 m (see also cities with the most skyscrapers). Shanghai's metro has surpassed Beijing's as the world's longest, at over 830 km.
Delhi, India · pop. 16,787,941
Delhi's metropolitan region, including Gurgaon, Noida and Ghaziabad, is now estimated by the UN at over 33 million people, and is widely projected to overtake Tokyo as the world's largest urban agglomeration before 2030 thanks to faster growth and Tokyo's demographic contraction.
The National Capital Region is administratively split between Delhi (a Union Territory), Haryana and Uttar Pradesh, which makes coordinated urban planning genuinely hard. The Delhi Metro, opened in 2002 and still expanding, is now one of the world's largest by route length, but the city's air quality remains a persistent crisis driven by vehicle traffic, construction dust and crop-burning on the upwind plains.
Tokyo, Japan · pop. 13,613,660
Greater Tokyo has held the world's #1 spot for decades, with roughly 37 million people across the Tokyo-Yokohama metropolitan area as measured by the UN World Urbanization Prospects. The figure includes commuter belts as far as Saitama, Chiba and Kanagawa, and it has been remarkably stable for twenty years as the city ages and the surrounding region contracts.
What keeps Tokyo functional at that scale is its commuter rail. Shinjuku Station alone handles 3.6 million passengers a day, and the combined JR East, Tokyo Metro, Toei and private-railway networks move more people per day than the entire population of Australia. See also our list of cities with the best public transit.
How we chose these
Population estimates for megacities vary wildly depending on whether you measure the administrative city, the urban agglomeration, or the wider metropolitan region. We used the United Nations Department of Economic and Social Affairs (DESA) World Urbanization Prospects definitions where possible, supplemented by national census data. The order reflects current UN figures; rankings shift slightly between the UN, Demographia, and OECD Functional Urban Areas datasets.
Sources & further reading
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For entertainment only. Rankings on this page are editorial picks compiled from public sources for fun and discovery — they aren't a scientific measurement. Population figures and place details come from open data; see the linked place pages for sources.