Hong Kong, officially the Hong Kong Special Administrative Region of the People's Republic of China, is an autonomous territory on the eastern side of the Pearl River estuary in South China. Along with Macau, Guangzhou, Shenzhen, Zhuhai, and several other major cities in Guangdong, the territory forms a core part of the Pearl River Delta metropolitan region, the most populated area in the world. With over 7.4 million Hongkongers of various nationalities in a territory of 1,104 square kilometres, Hong Kong is the fourth-most densely populated region in the world.
Hong Kong was formerly a colony of the British Empire, after Qing China ceded Hong Kong Island at the conclusion of the First Opium War in 1842. Originally a lightly populated area of farming and fishing villages, the territory has become one of the most significant financial centres and trade ports in the world. With the exception of the Second World War, during which the colony was occupied by the Empire of Japan, Hong Kong remained under British control until 1997, when it was returned to China. As a special administrative region, Hong Kong maintains a separate political and economic system apart from mainland China.