The most populous country in the world is China. As of the most recent estimates, China's population exceeds 1.4 billion people, making it the largest country by population. This vast population has resulted from decades of growth, influenced by various historical, social, and economic factors. China's government has implemented various policies over the years, such as the one-child policy, to manage growth. However, these policies have transitioned with changing demographics, aiming to balance population growth with sustainability and economic development. India is a close contender, with significant population growth rates as well.