World's Largest Cities
Thirty-three cities now have urban-agglomeration populations exceeding 10 million. Tokyo (37 million) leads but has been declining slowly; Delhi (32 million) is expected to overtake it by 2030. The fastest-growing megacities are in sub-Saharan Africa — Lagos, Kinshasa, Dar es Salaam — and in South Asia. By 2050, 13 of the world's 25 largest cities will be African.
Key insights
Tokyo's reign is ending — slowly
Tokyo's metropolitan population peaked at ~38M (2010) and has declined ~1M as Japan's aging accelerates. It remains the world's largest urban agglomeration but Delhi is projected to overtake it by 2030. The Tokyo decline reflects national-level demographics — Japan's overall population is falling, and Tokyo's inflow from rural areas can't fully compensate.
African urbanization is the demographic story of the century
Lagos is projected to exceed 30M by 2050 (from ~22M today). Kinshasa, Dar es Salaam, Luanda, Nairobi and Khartoum will join the megacity list. Sub-Saharan African urban populations are growing at 4%+/year — faster than any other region historically. Infrastructure investment is lagging far behind, producing some of the largest informal-settlement populations in history.
Urban definition matters enormously
Tokyo at 37M counts the Greater Tokyo metropolitan area. Tokyo as a city proper (23 wards) is 9.7M. New York as 'metropolitan' is 23M; as the city, 8.3M. These differ by factor of 2-4×. UN World Urbanization Prospects uses 'urban agglomeration' (continuous built-up area) which is the most meaningful — but country definitions vary, so the league table has wide uncertainty bands at the boundaries.
Top 25 urban agglomerations (2024)
Population in millions, UN WUP medium variant
Show data table
| Millions | |
|---|---|
| Tokyo | 37.4 |
| Delhi | 32 |
| Shanghai | 28.6 |
| Dhaka | 23.2 |
| São Paulo | 22.6 |
| Mexico City | 22.5 |
| Cairo | 22.2 |
| Beijing | 22 |
| Mumbai | 21.7 |
| Osaka | 19 |
| Karachi | 18 |
| Chongqing | 18 |
| Istanbul | 16 |
| Buenos Aires | 15.6 |
| Kolkata | 15.6 |
| Kinshasa | 17 |
| Lagos | 22 |
| Manila | 14.6 |
| Tianjin | 13.9 |
| Guangzhou | 14.5 |
| Rio | 13.6 |
| Lahore | 14 |
| Bangalore | 13.7 |
| Shenzhen | 12.8 |
| Moscow | 12.7 |
Key Finding: Asian megacities dominate the top 20. Lagos, Cairo, Kinshasa and Dhaka are the African and South Asian challengers rising fastest.
Projected fastest-growing megacities 2024–2050
Projected % increase in urban population
Show data table
| % growth 2024→2050 | |
|---|---|
| Dar es Salaam | 176 |
| Lagos | 107 |
| Kinshasa | 109 |
| Luanda | 116 |
| Khartoum | 140 |
| Niamey | 189 |
| Bamako | 140 |
| Kabul | 89 |
| Dhaka | 55 |
| Karachi | 67 |
| Cairo | 52 |
| Delhi | 33 |
Key Finding: Sub-Saharan African megacities will more than double; many will rank among the world's largest by 2050.
Methodology & caveats
Urban agglomeration vs city proper vs metro area
Urban agglomeration (UN): continuous built-up area regardless of administrative boundaries. City proper: legal/administrative city limits. Metropolitan area: economically integrated commuter region, varies by country. Rankings can shift dramatically depending on which is used.
Projection uncertainty
UN projections to 2050 use medium-fertility, medium-mortality, medium-urbanization assumptions. Actual outcomes have varied — Tokyo growth in 1990s exceeded forecasts; recent Lagos growth has too. Tail uncertainty is wide in sub-Saharan Africa where fertility decline pace remains unclear.
Megacity vs mega-region
Some adjacent metropolitan areas are now functionally integrated — Pearl River Delta (Hong Kong-Shenzhen-Guangzhou-Macao ~60M), BosWash corridor (Boston-New York-DC ~50M), Tokyo-Yokohama-Saitama-Chiba. These mega-regions are larger than any individual city but aren't standard rankings since they cross administrative boundaries.