Which of the following is not a country?

Macau, officially Macao, is the abbreviation of the Macao Special Administrative Region of the People's Republic of China, a special administrative region on the western side of the Pearl River estuary in southern China.

Macau was formerly a colony of the Portuguese Empire, after Ming China leased the territory as a trading post in 1557. Between 1557 and 1887, Macau was governed by the Portuguese under Chinese sovereignty and authority. In 1887, Portugal was given perpetual colonial rights for Macau. The colony remained under Portuguese rule until 1999, when it was transferred to China. As a special administrative region, Macau maintains separate governing and economic systems from that of mainland China.