According to the United Nations Population Division, the largest city in the world by population is Tokyo, with a population of 37.4 million. Due to an aging population and government incentive programs the population of the city is slowing going down. According to Wikipedia The cities in the world with the largest population are Tokyo, Delhi, Shanghai, São Paulo, Mexico City, Cairo, Mumbai, Beijing, Dhaka, Osaka, New York, Karachi, Buenos Aires, and Chongqing