Tianjin, formerly romanized as Tientsin, is a coastal metropolis in northern China and one of the four national central cities of the People's Republic of China (PRC), with a total population of 15,469,500, and is also the world's 11th-most populous city proper. It is governed as one of the four municipality under the direct administration of central government of the PRC and is thus under direct administration of the central government. Tianjin borders Hebei Province and Beijing Municipality, bounded to the east by the Bohai Gulf portion of the Yellow Sea. Part of the Bohai Economic Rim, it is the largest coastal city in northern China.