Tianjin (Chinese: 天津; pinyin: About this sound Tiānjīn), formerly known in English as Tientsin, is a metropolis in northern coastal Mainland China and one of the five national central cities of the country, with a total population of 15,469,500, and is also the world's 6th-most populous city proper. Part of the Bohai Economic Rim, it is the largest coastal city in northern China.