* China (People's Republic of China)
* Singapore
* Taiwan (Republic of China)
* Malaysia (along with English and Malay)
* Brunei (along with English and Malay)
It's important to note that:
* Hong Kong and Macau are Special Administrative Regions of China and use Cantonese as the primary language, though Mandarin is also widely understood.
* There are other dialects of Chinese spoken in various parts of the world, but Mandarin is the most widely spoken and understood.
If you're looking for countries where Chinese is spoken, but not necessarily official, the list would be significantly longer, including places like Thailand, Vietnam, Indonesia, and many more.