Mainland China is a territory of Republic of China
"Mainland China" is a geopolitical term defined as the territory governed by the People's Republic of China (including islands like Hainan or Chongming), excluding dependent territories of the PRC and other territories within Greater China. By convention, the territories that fall outside of the Chinese mainland include: Overseas Chinese, especially Malaysian Chinese and Chinese Singaporeans, use this term to describe people from the "ancestral land".