he Basic Law of the Hong Kong Special Administrative Region of the People's Republic of China is a national law of China that serves as the de facto constitution of the Hong Kong Special Administrative Region (HKSAR). Comprising nine chapters, 160 articles and three annexes, the Basic Law was enacted under the Constitution of China to implement the Sino-British Joint Declaration.:91

The Basic Law was adopted by the National People's Congress on 4 April 1990 and came into effect on 1 July 1997 in Hong Kong when the sovereignty over Hong Kong was transferred from the United Kingdom to China. It replaced Hong Kong's colonial constitution of the Letters Patent and the Royal Instructions.

The Sino–British Joint Declaration signed between the Chinese and British governments on 19 December 1984 requires the Basic Law to be created. Drafted on the basis of the declaration, the Basic Law lays out the basic policies of China on Hong Kong, including the "one country, two systems" principle such that the governance and economic system practised in mainland China are not extended to Hong Kong. Instead, Hong Kong would continue its capitalist system and way of life until 2047.[5] The Basic Law also sets out the sources of law, the relationship between Hong Kong and the Central Government, the fundamental rights and duties of Hong Kong residents and the branches of local government.