What is a Megacity?

🏗️ What is a Megacity?

A megacity is a city with a population of more than 10 million people. The term was first widely used in the 1970s, when planners began to recognise that cities of this scale created challenges that smaller urban areas simply did not face. A city of 500,000 needs a bus network and a water supply. A city of 22 million needs all of that, multiplied many times over — and it needs it to work simultaneously, every day, for people spread across hundreds of square kilometres.

The geography of megacities has changed dramatically in the last 70 years. In 1950, megacities were a feature of the wealthiest nations: New York and Tokyo. By 2024, the list looks very different:

Rank	City	Country	Population (2024)	Income Level
1	Tokyo	Japan	37.1 million	HIC
2	Delhi	India	35.2 million	NEE
3	Shanghai	China	29.0 million	NEE
4	Dhaka	Bangladesh	22.5 million	LIC
5	São Paulo	Brazil	22.2 million	NEE
6	Mumbai	India	21.4 million	NEE
7	Beijing	China	21.3 million	NEE

The critical geographical pattern: approximately 90% of megacity growth is now happening in LICs (Low Income Countries) and NEEs (Newly Emerging Economies) in Africa and Asia. Cities like Lagos, Kinshasa, and Karachi are projected to enter the megacity category within the next decade. This matters because growth in a wealthy country like Japan looks very different from growth in Bangladesh — the infrastructure, governance, and resources available to manage rapid urban expansion differ enormously.

The Speed of Change

Numbers alone do not convey how fast this transformation is happening. Delhi adds roughly one million people per year. Lagos has grown from 290,000 people in 1950 to over 15 million today — a fiftyfold increase in 70 years. No city in human history ever grew this fast, for this long, across this many different countries simultaneously. The infrastructure, planning, and governance systems that megacities need take decades to build. The populations arrive far faster than those systems can be created.