Waishengren (), sometimes called mainlanders, are a group of migrants who arrived in Taiwan from mainland China between the Japanese surrender at the end of World War II in 1945, and Kuomintang retreat and the end of the Chinese Civil War in 1949. They came from various regions of mainland China and spanned multiple social classes. The term is often seen in contrast with benshengren (), which refers to Hoklo and Hakka people in Taiwan who arrived prior to 1945 who had lived under Japanese rule. The term excludes other ethnic Chinese immigrants (e.g. from Malaysia or Hong Kong) and later immigrants from mainland China.
The formal definition of a waishengren () was someone living in Taiwan whose ancestral home, which is passed down through one's father, was not in Taiwan. By contrast, a benshengren () was someone whose ancestral home was Taiwan. By this formal definition, a person born in Taiwan whose father's ancestral home is not in Taiwan is considered a waishengren. Conversely, a person not born in Taiwan whose ancestral home is Taiwan (most notably Lien Chan) is considered a benshengren. Ancestral homes were eliminated in official records (e.g. on identity cards, household registrations, and passports) in 1996, and replaced with place of birth, which ended the official distinction of waishengren versus benshengren since many waishengren were born in Taiwan.
Today, in practice the term broadly refers to the cultural group of people who migrated from mainland China to Taiwan starting in 1945 when the Republic of China took control of Taiwan after the Surrender of Japan at the conclusion of World War II, and into the 1950s during the retreat of the Republic of China to Taiwan and its aftermath. Recent immigrants to Taiwan from China are not considered waishengren, but make up a separate social category. Due to significant intermarriage between waishengren and benshengren families, it is difficult to precisely define the distinction in later generations.