Megacities, metropolises and megalopolises

What the words used for big cities mean, and how the United Nations measures them.

Megacities in 2025

Becoming megacities by 2050 (projections)

Source: United Nations, World Urbanization Prospects 2025 (CC BY 3.0 IGO). After 2025, projections. Cities measured as the built-up, densely inhabited area (DEGURBA method). Before 1975 the UN only gives the number of cities by size class (file 34).

• BosWash (Northeast megalopolis)

  United States · 22 million inhabitants in its cities (UN, 2025)

  The first megalopolis described, by Jean Gottmann in 1961: from Boston to Washington, through New York, Philadelphia and Baltimore.

  Boston, New York City, Philadelphia, Baltimore, Washington, D.C.

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• Great Lakes

  United States and Canada · 17 million inhabitants in its cities (UN, 2025)

  Megaregion defined by the America 2050 project (Regional Plan Association). Its cities are further apart than in the other megalopolises.

  Chicago, Milwaukee, Grand Rapids, Indianapolis, Detroit, Windsor, Cincinnati, Columbus, Toledo, Pittsburgh, Buffalo, Rochester, Toronto, Ottawa, Montreal

  Not listed on their own in the UN data: Cleveland.

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• Pacific Belt (Taiheiyō)

  Japan · 63 million inhabitants in its cities (UN, 2025)

  From Tokyo to Fukuoka, along the Pacific coast. Its core is the Tōkaidō, between Tokyo, Nagoya and Osaka.

  Mito, Tsukuba, Tokyo, Numazu, Shizuoka, Hamamatsu, Toyohashi, Nagoya, Yokkaichi, Osaka, Himeji, Wakayama, Tokushima, Okayama, Takamatsu, Fukuyama, Hiroshima, Matsuyama, Kitakyūshū, Fukuoka, Ōita-shi

  Not listed on their own in the UN data: Yokohama, Kyoto, Kobe.

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• Pearl River Delta

  China · 51 million inhabitants in its cities (UN, 2025)

  The Greater Bay Area: nine cities of Guangdong with Hong Kong and Macao.

  Guangzhou railway station, Shenzhen, Zhongshan, Huizhou, Zhaoqing, Hong Kong, Macau

  Not listed on their own in the UN data: Foshan, Dongguan, Jiangmen.

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• Yangtze River Delta

  China · 78 million inhabitants in its cities (UN, 2025)

  The 26 cities of the Chinese government’s 2016 plan: a planning area more than a continuous urban belt.

  Shanghai, Nanjing, Zhenjiang, Yangzhou, Changzhou, Suzhou, Wuxi, Nantong, Taizhou, Yancheng, Hangzhou, Jiaxing, Huzhou, Ningbo, Zhoushan, Jinhua, Taizhou, Hefei, Wuhu, Chuzhou, Ma'anshan, Tongling, Chizhou, Anqing, Xuancheng

  Not listed on their own in the UN data: Shaoxing.

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• Jing-Jin-Ji (Beijing–Tianjin–Hebei)

  China · 34 million inhabitants in its cities (UN, 2025)

  Beijing, Tianjin and the main cities of Hebei province.

  Beijing, Tianjin, Shijiazhuang, Tangshan, Baoding, Qinhuangdao, Zhangjiakou, Cangzhou, Langfang, Chengde

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• Blue Banana

  Europe · 48 million inhabitants in its cities (UN, 2025)

  A concept by the geographer Roger Brunet (1989), debated: a 1991 study for the European Commission saw it as an idea rather than a reality. Brunet first left Paris out; later versions include it.

  Liverpool, Manchester, Leeds, Birmingham, London, Paris, Lille, Amsterdam, Rotterdam, The Hague, Utrecht, Brussels, Antwerp, Ghent, Essen, Dortmund, Düsseldorf, Cologne, Frankfurt, Mannheim, Stuttgart, Strasbourg, Basel, Zurich, Milan, Turin, Genoa

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• Rio de Janeiro–São Paulo

  Brazil · 35 million inhabitants in its cities (UN, 2025)

  Brazil’s two largest cities and those between them, along the Paraíba valley.

  São Paulo, Rio de Janeiro, Campinas, Santos, Sorocaba, São José dos Campos, Juiz de Fora, Jundiaí, Volta Redonda, Piracicaba, Campos dos Goytacazes, Petrópolis

  Not listed on their own in the UN data: Guarulhos, Niterói, São Gonçalo, Duque de Caxias.

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• Southern California

  United States and Mexico · 17 million inhabitants in its cities (UN, 2025)

  America 2050 megaregion, across the border to Tijuana. The source also includes Las Vegas, left out here because it is far away, across the desert.

  Los Angeles, Riverside, San Diego, Tijuana

  Not listed on their own in the UN data: San Bernardino.

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• Abidjan–Lagos Corridor

  Côte d’Ivoire, Ghana, Togo, Benin, Nigeria · 32 million inhabitants in its cities (UN, 2025)

  A string of cities along the coast of the Gulf of Guinea, across five countries.

  Abidjan, Sekondi-Takoradi, Cape Coast, Accra, Lomé, Cotonou, Porto-Novo, Lagos

  Not listed on their own in the UN data: Abomey-Calavi.

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