Macau or Macao (澳門, ; Macau ), 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 in an area of 32.9 km2, 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.
Originally a sparsely populated collection of coastal islands, 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. Although the city has one of the highest per capita incomes in the world, it has severe income inequality.
Macau has a very high Human Development Index and the fourth-highest life expectancy in the world. The territory is highly urbanised and most development is built on reclaimed land; two-thirds of total land area is reclaimed from the sea.
The first known written record of the name "Macau", rendered as "Ya/A Ma Gang" ("亞/阿-媽/馬-港"), is in a letter dated 20 November 1555. The local inhabitants believed that the sea goddess Mazu (alternatively called A-Ma) had blessed and protected the harbour and called the waters around A-Ma Temple using her name. When Portuguese explorers first arrived in the area and asked for the place name, the locals thought they were asking about the temple and told them it was "Ma Kok" (媽閣). The earliest Portuguese spelling for this was Amaquão. Multiple variations were used until Amacão / Amacao and Macão / Macao became common during the 17th century, gradually standardising as Macao, and Macau today.
Macau Peninsula had many names in Chinese, including Jingao (井澳/鏡澳), Haojing (濠鏡), and Haojingao (濠鏡澳). The islands Taipa, Coloane, and Hengqin were collectively called Shizimen (十字門). These names would later become Aomen (澳門), Oumún in Cantonese and translating as "bay gate" or "port gate", to refer to the whole territory.