Hong Kong (Chinese: 香港; literally: "Fragrant Harbour" or "Incense Harbour"), officially the Hong Kong Special Administrative Region of the People's Republic of China, is an autonomous territory on the Pearl River Delta in East Asia. The mainland Chinese province of Guangdong borders the territory to the north. With a total land area of 1,106 square kilometres (427 sq mi) and a population of over 7.3 million of various nationalities, it ranks as the world's fourth most densely populated sovereign state or territory.
After the First Opium War (1839–42), Hong Kong became a British colony with the perpetual cession of Hong Kong Island, followed by the Kowloon Peninsula in 1860 and a 99-year lease of the New Territories from 1898. Hong Kong was later occupied by Japan during the Second World War until British control resumed in 1945. In the early 1980s, negotiations between the United Kingdom and China resulted in the 1984 Sino-British Joint Declaration, which paved way for the transfer of sovereignty of Hong Kong in 1997, when it became a special administrative region (SAR) with a high degree of autonomy.
Under the principle of "one country, two systems", Hong Kong maintains a separate political and economic system from China. Except in military defence and foreign affairs, Hong Kong maintains its independent executive, legislative and judiciary powers. In addition, Hong Kong develops relations directly with foreign states and international organisations in a broad range of "appropriate fields".
Hong Kong is one of the world's most significant financial centres, with the highest Financial Development Index score and consistently ranks as the world's most competitive and most laissez-faire economic entity in the World Competitiveness Yearbook. Its legal tender, the Hong Kong dollar, is the world's 13th most traded currency. Hong Kong's tertiary sector dominated economy is characterised by simple taxation with a competitive level of corporate tax and supported by international confidence in its independent judiciary system where the rule of law, not rule by law, applies to legal, contractual proceedings. However, while Hong Kong has one of the highest per capita incomes in the world, it suffers from the most severe income inequality among developed economies.
Hong Kong is renowned for its deep natural harbour, which enables ready access by international cargo ships, and its skyline, with a very high density of skyscrapers; the territory boasts the second largest number of high rises of any city in the world. It has a very high Human Development Index ranking and the world's longest life expectancy. Over 90% of the population makes use of well-developed public transportation. Seasonal air pollution with origins from neighbouring industrial areas of Mainland China, which adopts loose emissions standards, has resulted in a high level of atmospheric particulates.