mainland China

Short definition from Wiktionary

Proper noun

1. 1
   The People's Republic of China, viewed as the general geographical region administered by the PRC in the aftermath of the Chinese Civil War (as opposed to Hong Kong, Macau, and Taiwan which are coastal and insular areas)
2. 2
   Also used other than figuratively or idiomatically: see mainland, China.
3. 3
   Alternative letter-case form of mainland China.