They’re three separate places in the greater Tokyo region, but they’re often mentally lumped together because the metropolitan area is enormous.
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Narita is a city in Chiba Prefecture, east of Tokyo. It is best known because Narita International Airport is located there, roughly 60 km (37 mi) east of central Tokyo. So “Narita Airport” does not mean an airport actually in Tokyo.
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Tokyo is the huge capital metropolis on the western side of Tokyo Bay. Strictly speaking, Tokyo is a prefecture/metropolitan government area rather than a single ordinary city. Central Tokyo includes places such as Shinjuku, Shibuya, Ginza and Tokyo Station.
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Yokohama is a separate major city in Kanagawa Prefecture, immediately south of Tokyo on Tokyo Bay. It is about 30 km (19 mi) from central Tokyo and has a population of roughly 3.7 million.
A useful mental picture is:
Narita → Tokyo → Yokohama
east → west/southwest
More precisely, Narita is northeast/east of Tokyo, while Yokohama is south/southwest of Tokyo, with Tokyo Bay between portions of the three.
The interesting wrinkle is that Tokyo and Yokohama are effectively one continuous urban megaregion. You can travel from central Tokyo into Yokohama without encountering anything resembling a rural boundary. Narita, by contrast, is distinctly farther out and has more countryside around it.
If you're asking because of Japanese geography or travel, I can also explain why Tokyo has both Haneda and Narita airports, and when you would use each.
Yes—and this is where the Tokyo–Yokohama combination becomes especially interesting. The answer depends quite a bit on what you count as the urban area, because administrative boundaries and continuously built-up areas don't coincide.
Using the UN's latest standardized definition of an urban agglomeration, Tokyo itself is about 33.4 million people in 2025. The UN now ranks it third in the world, behind Jakarta (41.9 million) and Dhaka (36.6 million).
But another widely used urban-area definition specifically treats Tokyo–Yokohama as a single built-up urban area and puts it at about 37 million.
So I'd describe the broader Tokyo–Yokohama urban complex as roughly 35–37 million people, rather than pretend there is one uniquely correct number.
How that stacks up
| Urban region | Approx. 2025 population |
|---|---|
| Jakarta | 41.9 million |
| Dhaka | 36.6 million |
| Tokyo | 33.4 million |
| New Delhi | 30.2 million |
| Shanghai | 29.6 million |
| Guangzhou | 27.6 million |
| Cairo | 25.6 million |
| Manila | 24.7 million |
| Kolkata | 22.6 million |
| Seoul | 22.5 million |
Those are the UN's comparable urban-agglomeration figures.
The striking thing is that Tokyo–Yokohama is not merely a very large city; it's an urban system of extraordinary scale. Tokyo and Yokohama are separate municipalities, but their built-up areas essentially run together. And the metropolitan area extends considerably farther—to Chiba, Saitama and other surrounding cities—so the 35–37 million figure isn't even the most expansive possible definition.
There's also an interesting historical twist: Tokyo used to be unambiguously #1. The UN estimated about 30.3 million in 2000. Since then, Tokyo has grown only modestly, while Jakarta and Dhaka have exploded in population. The UN projects Tokyo's urban-agglomeration population to actually decline to about 30.7 million by 2050.
So your original three-place question has a rather impressive answer: Narita–Tokyo–Yokohama sits on the edge of one of the largest concentrations of humanity ever created, with something on the order of 35 million people in the continuously connected Tokyo–Yokohama urban system.
Yes. And this comparison brings out an important distinction: Tokyo–Yokohama and the Northeast Megalopolis are not quite the same kind of thing. Tokyo is an exceptionally concentrated metropolitan region; the American Northeast is a long chain of major cities that have grown into one enormous urban corridor.
Using roughly comparable 2025 population concepts, I'd put them like this:
| Urban region | Approx. population | Character |
|---|---|---|
| Tokyo–Yokohama / greater Tokyo | ~35–37 million | One enormous, highly integrated metropolitan region |
| Northeast Megalopolis (Boston–NY–Philadelphia–Baltimore–Washington) | ~45–50 million | A ~600-km chain of separate metropolitan areas |
| Mexico City | ~23 million | Very large, concentrated metropolitan area |
| São Paulo | ~23 million | Very large, concentrated metropolitan area |
The UN's new 2025 methodology puts the Tokyo urban agglomeration at 33.4 million, while Mexico City and São Paulo are no longer among its ten largest under that particular internationally harmonized definition.
The really interesting comparison: Tokyo vs. BosWash
The Northeast Megalopolis—often called BosWash—is geographically much larger.
Think:
Boston → Providence → Hartford/New Haven → New York → Philadelphia → Baltimore → Washington
That's roughly 600–700 km (375–435 miles) of almost continuous urbanized territory, depending on where you draw the boundaries.
Tokyo's giant urban region is different. It has an enormous central core, with Tokyo, Yokohama, Kawasaki, Saitama, Chiba and numerous other cities essentially merging into one urban organism. Narita sits farther out but is economically tied to it.
So although BosWash can contain more people in the broadest definition, Tokyo produces the impression of a much larger single city. There is no American equivalent of getting on a commuter train in Tokyo and finding yourself traveling through an almost uninterrupted urban landscape for hours.
And Mexico City and São Paulo?
They're closer to Tokyo in structure.
Mexico City is an enormous basin-centered metropolis. The metropolitan area has roughly the same order of population as São Paulo—about 23 million under commonly used metropolitan definitions. One can reasonably call each a single gigantic metropolitan area.
São Paulo is similar, although its urbanized area spreads over a very large region and incorporates numerous municipalities. It's an especially good comparison with Tokyo in the sense that what looks administratively like many cities functions economically as one huge metropolitan system.
But Tokyo is in another league in terms of rail-based integration and population density.
One amusing way of putting it:
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Mexico City: one gigantic city
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São Paulo: one gigantic city
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Tokyo: one gigantic city pretending to be dozens of cities
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BosWash: dozens of major cities that have largely grown into one gigantic corridor
And there's a demographic surprise: Tokyo isn't the growing monster anymore. The UN's 2025 figures have Tokyo at 33.4 million and projecting a decline to about 30.7 million by 2050. Jakarta and Dhaka have now overtaken it.
The Northeast Megalopolis is particularly interesting because its population is spread among several genuinely major cities, whereas Tokyo's enormous population is concentrated much more heavily around one dominant metropolitan center.
If you want, I can also compare these four by physical size and population density—that produces an even more striking picture.
Europe is actually a useful contrast, because Europe doesn't have a Tokyo-sized single metropolitan area. It has several large metros, plus one particularly interesting polycentric urban corridor.
Using the UN's 2025 urban-agglomeration figures for a reasonably consistent comparison:
| Urban system | Approx. population | What it is |
|---|---|---|
| Tokyo | 33.4m | One dominant megacity |
| Lagos | ~12.8m | Fast-growing megacity |
| London | 10.4m | Large single metropolitan area |
| Paris | 9.4m | Large single metropolitan area |
| Rhine-Ruhr | ~10–12m | Polycentric German urban region |
| Milan | ~6m | Major northern Italian metro |
| Madrid | ~6–7m | Major Spanish metro |
| São Paulo | ~23m | Huge Brazilian metro |
| Mexico City | ~23m | Huge Mexican metro |
The UN's 2025 urban-agglomeration methodology, for example, gives London 10.416 million and Paris 9.382 million.
Lagos is the fascinating one
Lagos is already enormous, but it is nowhere near Tokyo yet. Depending on the boundary used, you'll encounter estimates ranging from roughly 13 million to well over 20 million. That's not necessarily disagreement about the number of people; it's largely disagreement about where Lagos ends.
And Lagos is growing extraordinarily rapidly. Unlike Tokyo, which is aging and beginning to shrink, Lagos is part of one of the world's great demographic explosions.
That's the big geographical divide:
Tokyo:
33m → slowly shrinking
Lagos:
~13–20m → rapidly growing
Paris/London:
~9–10m → mature, relatively stable metropolitan regions
São Paulo/Mexico City:
~23m → enormous mature megacities, with much slower growth than Lagos
Europe has one thing the others don't
If we broaden the concept from "a metropolitan area" to "a megalopolis", Europe becomes much more interesting.
The Rhine-Ruhr region in Germany runs roughly:
Düsseldorf → Essen → Dortmund → Duisburg → Cologne → Bonn
There isn't one dominant city. Instead, you have a dense constellation of cities, industrial towns and suburbs that have effectively grown together.
And farther west you can think of a still larger European urban network running through:
Amsterdam → Rotterdam → Antwerp → Brussels → Cologne/Rhine-Ruhr
That's sometimes described in terms of the Blue Banana, although that's a somewhat loose economic-geographical concept rather than a single continuously urbanized city.
So I'd revise the mental picture from our previous discussion:
- Tokyo: the world's great single-core megacity.
- Northeast US: an enormous linear megalopolis of separate major cities.
- Rhine–Ruhr/Benelux: Europe's equivalent polycentric urban system.
- Mexico City/São Paulo: enormous single metropolitan concentrations.
- Lagos: the rapidly emerging African giant, whose eventual scale is much harder to predict.
And there's a wonderful irony here: Europe has some of the world's densest urban networks, but not one of the world's giant 30-million-person megacities.
Tokyo achieves roughly 35 million people in an area that feels like one coherent city, while Southern California achieves perhaps two-thirds as many people spread over an astonishingly large landscape of separate but interconnected cities.
Exactly. Southern California belongs in this discussion, although it is another case where the word megalopolis can be more useful than city.
The urbanized area running roughly
Santa Barbara → Los Angeles → Orange County → San Diego → Tijuana
contains something like 20–25 million people, depending heavily on the boundaries you choose.
And it has a very different physical form from Tokyo.
| Region | Rough population | Urban form |
|---|---|---|
| Greater Tokyo | 33–37m | Extremely dense, rail-oriented, enormous core |
| Northeast US | 45–50m | Linear chain of major metros |
| Southern California | 20–25m | Vast, dispersed, multi-centered |
| Mexico City | ~23m | Huge concentrated metro |
| São Paulo | ~23m | Huge concentrated metro |
| Lagos | ~13–20m | Rapidly expanding megacity |
| Rhine–Ruhr/Benelux | ~15–25m* | Polycentric European network |
*Very boundary-dependent.
Southern California is particularly deceptive because Los Angeles isn't really "the city" in the way the name suggests. The Los Angeles metropolitan area contains a multitude of substantial cities—Long Beach, Anaheim, Santa Ana, Irvine, Riverside, San Bernardino, etc.—and then San Diego is another major metropolitan center farther south.
There's also a geographical barrier that makes the comparison fascinating: mountains and desert constrain the habitable corridor, while the Pacific Ocean forms the western edge. Consequently, the developed strip is enormous north-to-south but relatively constrained east-to-west.
And then there's Tijuana, which makes the region genuinely transnational. The San Diego–Tijuana urban area is one of the world's largest binational metropolitan regions.
So if we're making a list of the world's great urban regions rather than merely cities, I'd definitely put Southern California in the conversation with Tokyo, BosWash, the Pearl River Delta, the Rhine–Ruhr/Benelux system, and the São Paulo region.
The really remarkable thing is that Tokyo achieves roughly 35 million people in an area that feels like one coherent city, while Southern California achieves perhaps two-thirds as many people spread over an astonishingly large landscape of separate but interconnected cities.
