A megacity is an urban area with a population over 10 million people. On the AP Human Geography exam (EK PSO-6.A.3), megacities are spatial outcomes of rapid urbanization that are increasingly located in periphery and semiperiphery countries, like Lagos, Dhaka, and São Paulo.
A megacity is defined by one number. If an urban area has more than 10 million people, it's a megacity. That's the whole test. Examples include Lagos, Mumbai, Dhaka, Mexico City, São Paulo, and Cairo.
The AP-relevant part isn't the number, though. It's the pattern. The CED (EK PSO-6.A.3) emphasizes that megacities and metacities are 'distinct spatial outcomes of urbanization increasingly located in countries of the periphery and semiperiphery.' In other words, the fastest-growing giant cities today are not New York and London. They're cities in less developed regions, where rural-to-urban migration and high population growth pile millions of people into urban areas faster than housing, water, sewage, and transit systems can keep up. That mismatch is why megacities show up again in Topic 6.8 as sustainability challenges, often paired with informal settlements (squatter settlements) on exam questions.
Megacities live in Unit 6 (Cities and Urban Land-Use Patterns and Processes), and they tie together three learning objectives. Under 6.1.A and 6.2.A, you explain the processes that drive urbanization, and megacities are the most dramatic result of those processes (migration, population growth, economic development). EK PSO-6.A.3 names megacities directly, so this is testable vocabulary, not optional trivia. Under 6.3.A, megacities help you talk about the global urban hierarchy, because a huge city is not automatically a globally powerful one. And under 6.8.A and 6.8.B, megacities are the setting where sustainability problems (sprawl, pollution, housing shortages) get most extreme. If a question asks you to connect urbanization to development patterns, megacities are your go-to example.
Keep studying AP Human Geography Unit 6
Global City (Unit 6)
This is the pairing the exam loves to test. A megacity is big; a global (world) city is powerful. Tokyo is both. Dhaka is a megacity but not a world city, and Zurich is a world city that's nowhere near 10 million people. Size and influence are two separate axes.
Urbanization (Unit 6)
Megacities are what urbanization looks like when it runs at full speed. The drivers in EK PSO-6.A.2 (migration, population growth, economic development, government policy) explain why these giant urban areas keep forming, especially in the developing world.
Sustainable Development (Units 6-7)
When 10+ million people share one urban area, every sustainability problem scales up. Megacities give you concrete examples for Topic 6.8 questions about why cities need smart-growth policies, better transit, and improved housing options.
Core-Periphery and World-Systems Theory (Unit 7)
The CED's claim that megacities are 'increasingly located in the periphery and semiperiphery' uses world-systems vocabulary straight out of Unit 7. This is a cross-unit link worth memorizing, because it lets you connect urban patterns to global development patterns in one sentence.
Megacity is most often a multiple-choice term. Stems typically ask you to identify which city qualifies as a megacity, distinguish a megacity from a metacity, or pick the right term for a city's role in the global urban hierarchy (where the answer is world city, not megacity, because the question is about influence rather than size). The trap answers are almost always metacity and world city, so know all three definitions cold. No released FRQ has used the term verbatim, but megacities are a strong example bank for free-response questions about urbanization in developing countries, squatter settlements, or urban sustainability challenges under Topics 6.2 and 6.8. If an FRQ asks you to describe a challenge of rapid urbanization in the periphery, naming a specific megacity like Lagos or Dhaka makes your answer concrete.
Both are size categories, and the CED lists them side by side in EK PSO-6.A.3. A megacity has more than 10 million people. A metacity has more than 20 million, so every metacity is also a megacity, but not the reverse. Tokyo is a metacity; Bogotá is a megacity. Multiple-choice questions test exactly this threshold, so memorize 10 million versus 20 million.
A megacity is an urban area with a population over 10 million people, and that single threshold is the definition.
A metacity is bigger, with over 20 million people, so every metacity counts as a megacity but not every megacity is a metacity.
The CED stresses that megacities are increasingly located in periphery and semiperiphery countries, which links Unit 6 urbanization to Unit 7 development theory.
Megacity measures size while world city measures influence, so a city can be one, both, or neither.
Megacities grow from rapid rural-to-urban migration and population growth, often outpacing infrastructure and creating the sustainability challenges tested in Topic 6.8.
A megacity is an urban area with a population over 10 million people. The CED (EK PSO-6.A.3) frames megacities as spatial outcomes of urbanization that are increasingly found in periphery and semiperiphery countries, like Lagos, Dhaka, and Mexico City.
It's a population cutoff. Megacities have over 10 million people, while metacities have over 20 million. Tokyo qualifies as a metacity; a city like Bogotá is a megacity but not a metacity.
No. Megacity measures population size, while world city (global city) measures economic and cultural influence at the top of the urban hierarchy. Dhaka is a megacity without world-city status, and many world cities like Zurich never reach 10 million people.
No, but the trend points that way. Tokyo, New York, and Osaka are megacities in the core, but the CED emphasizes that megacities are increasingly located in the periphery and semiperiphery, where urbanization is happening fastest.
Because population growth outruns infrastructure. When migration adds millions of residents faster than housing, water, sewage, and transit can expand, you get informal settlements, congestion, and pollution. That's why megacities pair so well with Topic 6.8 urban sustainability questions.