Macau or Macao (/məˈkaʊ/ (listen); Chinese: 澳門, Cantonese: [ōu.mǔːn]; Portuguese: Macau [mɐˈkaw]), officially the Macao Special Administrative Region of the People's Republic of China, is a special administrative region on the western side of the Pearl River estuary in southern China. With a population of 653,100^[3] and an area of 32.9 km² (12.7 sq mi), it is the most densely populated region in the world.

Macau was formerly a colony of the Portuguese Empire, after Ming China leased the territory as a trading post in 1557. Originally governing under Chinese authority and sovereignty, Portugal was given perpetual occupation rights for Macau in 1887. The colony remained under Portuguese control until 1999, when it was returned to China. As a special administrative region, Macau's system of government is separate from that of mainland China.^[6]

Originally a sparsely populated collection of coastal islands,^[7] the territory has become a major resort city and the top destination for gambling tourism. It is the ninth-highest recipient of tourism revenue and its gaming industry is seven times larger than that of Las Vegas.^[8] Although the city has one of the highest per capita incomes in the world, it has severe income inequality.^[9]

Macau has a very high Human Development Index^[5] and the fourth-highest life expectancy in the world.^[10] The territory is highly urbanised and most development is built on reclaimed land; two-thirds of total land area is reclaimed from the sea.^[11]