The 20 Most Populous Capital Cities in 2026

A handful of national capitals are bigger than entire countries. Tokyo's metropolitan area alone contains more people than Australia. Cairo's metro is more populous than Sweden. Here are the 20 largest capital cities on Earth — with the methodology that explains why the rankings shift so much depending on who is counting.

A note on how we measure

Cities can be measured three ways. The city proper is the official municipal boundary, often arbitrary — Tokyo's 23 wards have just 9 million people, but no one really thinks of those wards as "Tokyo." The urban area is the contiguous built-up zone regardless of municipal boundaries. The metropolitan area includes the urban core plus the surrounding commuter belt. The numbers below use metropolitan area, the most widely cited figure, drawn from the UN World Urbanization Prospects and major demographic agencies.

The top 5

Tokyo has been the largest capital on Earth for decades and continues to lead despite Japan's overall population decline — the metropolitan region keeps absorbing people from the rest of the country. Delhi may overtake it within a decade. Jakarta and Greater Jakarta combined ("Jabodetabek") is now one of the largest urban agglomerations of any kind on Earth, even though Indonesia is mid-transition to a new planned capital, Nusantara, on Borneo.

Ranks 6–10

Six of the top ten capitals are in Asia. Cairo is the largest African capital, anchoring a metropolitan population larger than most European countries. Mexico City sits on a former lakebed at 2,240 metres above sea level and continues to sink several centimetres a year as it pumps groundwater. Buenos Aires is the only South American capital in the top 10.

Ranks 11–15

Kinshasa's growth is the most dramatic in this range — it was a small administrative town under Belgian rule and now exceeds 16 million, rivalling London. The two Congos' capitals (Kinshasa, DR Congo, and Brazzaville, Republic of Congo) face each other across the Congo River and together form one of the largest combined urban areas on Earth.

Ranks 16–20

Paris's metro population is comparable to Lima or Bangkok, but it sits at #20 here because rankings between 11 and 25 are so close that a small difference in methodology shuffles them. Riyadh has been one of the fastest-growing capitals on Earth: in 1950 it had under 100,000 residents; today it has more than 7 million.

Big cities that aren't on this list

Two of the largest cities in the world are not capitals — and so they don't appear:

• Shanghai (~28 million metro) — the largest non-capital city on Earth, and far larger than China's actual capital, Beijing.
• Mumbai (~22 million metro) — India's largest city, but India's capital is Delhi.
• Lagos (~21 million metro) — was Nigeria's capital until 1991, when the role moved to the smaller, planned Abuja.
• São Paulo (~22 million metro) — Brazil's largest city; the capital, Brasília, has only ~5 million.
• Karachi (~17 million metro) — Pakistan's largest city; the capital is the much smaller Islamabad.

Five of the world's largest cities are not capitals — and that's exactly the pattern the world capitals guide tracks: many countries deliberately picked a smaller city for the capital so no single metropolis would dominate.

Why some capitals are huge and others tiny

The biggest capitals tend to be in countries with three traits: large population overall (so the capital captures a big slice), centralised political and economic power (no rival cities draw people away), and limited urban planning constraints (cities can sprawl). Tokyo, Cairo, Mexico City, and Jakarta all check those boxes.

The smallest capitals usually fail at least two of those tests. Wellington (New Zealand), Bern (Switzerland), Ottawa (Canada), Canberra (Australia), and Brasília (Brazil) all sit in countries where the capital was deliberately placed away from a larger city. Their metros stay small because the economic centre is somewhere else.