Macau is a territory of Republic of China
Macau (traditional Chinese: 澳門 simplified Chinese: 澳门) is a Special Administrative Region (SAR) of the People's Republic of China. Located across the Pearl River estuary from Hong Kong, Macau was until 1999 an overseas territory of Portugal. One of the world's most densely populated spots, Macau generates more revenue from gambling than anywhere else on the planet, including more than seven times the revenue generated by "The Strip" in Las Vegas. [...] Macau has a separate immigration regime from mainland China and Hong Kong. All travelers from mainland China and Hong Kong and all foreign countries have to go through immigration and customs checks on arrival in Macau. Therefore, if you want to reenter Mainland China from Macau, you will have to re-apply for another Chinese visa unless your existing one is a multiple entry visa. While Hong Kong and likewise Macau are officially part of the People's Republic of China, don't let this cause confusion, as they are still designated as SAR or Special Administrative Regions operating under their own immigration controls, currencies and autonomous governments. Furthermore, an entry permit to Hong Kong is not valid in Macau and vice versa. [...] Use caution with US carriers offering overseas plans, as Macau is considered a separate country from China or Hong Kong. Some plans, such as Verizon's TravelPass, do not include Macau.