With a population of over 1.3 billion people, China is the largest country by population in the world, as of 2015. India has a population of over 1.2 billion people and is therefore the second-largest country by population, and the United States follows third with a population of 316 million.
Indonesia, Brazil, Pakistan, Nigeria and Bangladesh are also in the top 10 of largest countries by population. The Population Reference Bureau predicts India to become the largest country by population in the world by 2050, with China following second. It also reports that the population of Democratic Republic of Congo and Ethiopia are on the rise, and that those countries are likely to be in the top 10 by 2050.