The country with over 100 million people that is most often cited as having the fastest population growth is Nigeria. It has also been one of the world’s fastest-growing large populations for years, while countries like the United States and Egypt have much larger total populations but slower growth rates.

Quick Scoop

If you mean fastest-growing population among countries with 100+ million people , Nigeria is the strongest answer from the available data. A large- population country can grow quickly either because of high birth rates, a young population, or both, and Nigeria fits that pattern.

Why Nigeria

  • Nigeria is far above the 100 million threshold and remains one of the world’s most rapidly expanding populations.
  • Countries such as the United States are large, but their growth rate is much lower than Nigeria’s.
  • Egypt is also over 100 million people, but its growth is not typically the fastest among that group.

Simple takeaway

So, the short answer is: Nigeria.

Note: “fastest growing” can mean either total annual increase or percentage growth rate. If you want, I can narrow it to the latest official estimate by growth rate or by absolute population increase.