* China (People's Republic of China): Mandarin is the official language of mainland China and is spoken by the majority of the population.
* Taiwan (Republic of China): While Taiwan has its own unique dialect of Mandarin, it is officially recognized as the standard language.
* Singapore: Mandarin is one of the four official languages of Singapore, alongside English, Malay, and Tamil.
* Malaysia: Mandarin is one of the eleven official languages of Malaysia, alongside Malay, English, and others.
* Brunei: Mandarin is one of the official languages of Brunei, alongside Malay and English.
It's important to note that "official language" can mean different things in different countries. In some cases, it may simply mean that the government uses the language for official purposes, while in other cases it may be the language most commonly spoken by the population.