A megacity is an urban area with a population over 10 million people. Per the AP Human Geography CED (EK PSO-6.A.3), megacities are distinct spatial outcomes of urbanization that are increasingly located in countries of the periphery and semiperiphery, like Lagos, Mumbai, and São Paulo.
A megacity is an urban area with more than 10 million residents. The definition is purely about population size, not wealth, influence, or how nice the skyline looks. That matters, because the AP exam's favorite fact about megacities is where they're growing. According to EK PSO-6.A.3, megacities (and their bigger siblings, metacities, with 20+ million people) are increasingly located in countries of the periphery and semiperiphery, places like Lagos, Dhaka, Mumbai, Jakarta, and São Paulo, not just core countries.
Why there? Rapid rural-to-urban migration plus high natural increase pile millions of people into cities faster than governments can build infrastructure. The result is often overurbanization, where the city's population outgrows its housing, jobs, sanitation, and services. So when you see "megacity" on the exam, think two things at once. First, a number (10 million). Second, a process (rapid urbanization in developing regions and the strain that comes with it).
Megacities live in Topic 6.2 (Cities Across the World) under learning objective 6.2.A, which asks you to explain the processes that drive urbanization. EK PSO-6.A.3 names megacities directly, which makes this one of the most quotable pieces of essential knowledge in Unit 6. But the term earns its keep across units. In Unit 2, megacities are walking examples of LO 2.2.A, since cramming 10+ million people into one area stresses services, infrastructure, and carrying capacity (EK PSO-2.D.1 and PSO-2.D.2). They're also products of migration, connecting to LO 2.12.A on the political, economic, and cultural effects of migration. And in Topic 6.9, megacities are where geographers put census data and field narratives to work tracking urban change (LO 6.9.A). If the exam wants a real-world setting for almost any population or urban concept, a megacity is the go-to stage.
Keep studying AP Human Geography Unit 6
Urbanization (Unit 6)
Megacities don't appear out of nowhere. They're what urbanization looks like when it runs at full speed. EK PSO-6.A.3 frames megacities as the spatial outcome of the urbanization process, so the cause-and-effect chain (rural-to-urban migration → urban growth → megacity) is exactly the kind of reasoning FRQs reward.
Global City (Unit 6)
These two get mixed up constantly, but they measure different things. Megacity is about population size (10 million+). Global city is about economic and political influence in the world system. Tokyo is both. Lagos is a megacity but not a top-tier global city. Zurich is a global city that's nowhere near megacity size.
Consequences of Population Distribution (Unit 2)
Megacities are Topic 2.2 in concentrated form. When 10+ million people share one urban area, the provision of services like medical care gets strained (EK PSO-2.D.1) and the environment feels the pressure of carrying capacity (EK PSO-2.D.2). A megacity is the ultimate test case for density's effects on society.
Effects of Migration (Unit 2)
Most megacity growth in the periphery comes from rural-to-urban migration, not just births. That migration brings the political, economic, and cultural effects from LO 2.12.A, including squatter settlements, informal economies, and new ethnic neighborhoods that reshape the cultural landscape (which loops in Topic 3.3).
Megacities show up most often in multiple-choice questions, usually testing one of three things. First, the definition itself (10 million or more people). Second, the location pattern, meaning you should recognize that new megacities are concentrated in the periphery and semiperiphery, so expect answer choices naming Lagos, Dhaka, Jakarta, or Mumbai rather than Paris or Chicago. Third, site and situation factors, like a practice question asking why coastal cities such as Shanghai and Lagos grew so large (access to water bodies for trade is the answer). No released FRQ has used "megacity" verbatim, but the concept is prime FRQ material for questions about urbanization challenges, overurbanization, squatter settlements, or how urban data tracks population change. If an FRQ asks you to explain a consequence of rapid urban growth in a developing country, naming a real megacity as your example earns you specificity points.
Both appear in the same CED bullet (EK PSO-6.A.3), and the only difference is the population threshold. A megacity has more than 10 million people; a metacity has more than 20 million. Every metacity (like Tokyo or Delhi) is also a megacity, but not the reverse. If an MCQ gives you a city of 22 million, the most precise label is metacity.
A megacity is an urban area with more than 10 million people, and a metacity is one with more than 20 million.
Per EK PSO-6.A.3, new megacities are increasingly located in periphery and semiperiphery countries, such as Lagos, Dhaka, Mumbai, and Jakarta.
Megacity growth is driven by rapid rural-to-urban migration combined with high natural increase, which often outpaces infrastructure and causes overurbanization.
Megacity is a population-size label, while global city is an influence label, so a city can be one without being the other.
Megacities concentrate the consequences of population density from Topic 2.2, including strained services, housing shortages, and pressure on carrying capacity.
Many large megacities, like Shanghai and Lagos, grew on coasts because access to water bodies supported trade and attracted population.
A megacity is an urban area with a population over 10 million people. The CED (EK PSO-6.A.3) emphasizes that megacities are spatial outcomes of urbanization that are increasingly found in periphery and semiperiphery countries.
No, and that's the exact misconception the exam targets. While Tokyo and New York are megacities, the fastest-growing ones are in the periphery and semiperiphery, including Lagos, Dhaka, Jakarta, and Mumbai, where rural-to-urban migration drives explosive growth.
A megacity is defined by size (10+ million people), while a global city is defined by influence over the world economy, like hosting major financial markets and corporate headquarters. Tokyo is both, Lagos is a megacity but not a leading global city, and Zurich is a global city far below megacity size.
It's just the population cutoff. A megacity has more than 10 million people, while a metacity has more than 20 million, so every metacity is also a megacity. Both terms appear together in EK PSO-6.A.3.
Access to water bodies. Coastal locations supported trade, ports, and economic activity, which attracted migrants and concentrated population there. This is a classic Unit 2 question about physical factors influencing population distribution (EK PSO-2.A.1).