Biggest City in the World: Population, Size, and What Really Matters

When people ask what the biggest city in the world, a term often used to describe the most populous urban area on Earth. Also known as largest city by population, it's not just about numbers—it's about how millions of people share space, transport, water, and air every single day. The answer changes depending on how you measure it. Some count only city limits. Others look at the whole urban sprawl—the packed suburbs, commuter belts, and connected towns that act like one giant machine. That’s why Tokyo keeps showing up at the top: over 37 million people live in its greater metro area. But Delhi isn’t far behind, and Lagos is growing faster than almost any other place on Earth.

Size isn’t just about headcount. The urban density, how tightly packed people are within a given area. Also known as population density, it determines whether a city feels like a crush or a crowd. Tokyo has high density but also world-class transit—trains run on time, platforms stay clean, and you can get anywhere without a car. Compare that to Dhaka, where density is even higher but roads are choked, and water access is unreliable. Then there’s Mexico City, where the skyline stretches for miles but power outages hit neighborhoods for hours. The megacity, an urban area with more than 10 million residents. Also known as metropolis, it’s not just a label—it’s a pressure test for infrastructure, housing, and government. A city can be huge on paper but still fail its people if the basics don’t work.

What you won’t find in most rankings is the real story behind the numbers. Why does Jakarta flood every rainy season? Why does São Paulo have one of the world’s highest income gaps despite being a global financial hub? Why does Cairo’s population keep growing even as its water supply shrinks? These aren’t just statistics—they’re daily struggles. The biggest city in the world isn’t the one with the most people. It’s the one where the most people are trying to survive, adapt, and build something better, despite the odds.

Below, you’ll find real stories from places that define what urban life looks like today—from the quiet survival of local news in shrinking towns to how global media covers the chaos of growing cities. These aren’t just headlines. They’re snapshots of how the world’s largest urban centers are changing, cracking, and holding together.