The first occupants of Taiwan were the ancestors of today’s Aborigines, who account for one to two percent of the population. Little is known about he origins of Taiwan’s first residents on when and why they came to the island. Most anthropologists believe that the Aborigines are Malayo-Polynesian people, related to the indigenous people of the Cordillera mountains of northern Luzon, the closest island of the Philippines. There are nine distinct ethnic group among Today’s Aborigines, each with its own language and culture. Many of the immigrants from China who began arriving in the 14th century intermarried with the Aborigines, as did the European settlers who occupied Taiwan during the 17th century.

The waves of later immigrants are thought to have driven many of the Aborigines into the high mountains.  Today, Aboriginies are still often called "mountain people," a term they consider derogatory.  Many of them never went into the highlands, living instead on the southern and eastern coastal plains.  In recent years, a majority of the highland Aborigines have migrated to the plains in search of work.

The first new immigrants to come to Taiwan were Han people, members of China’s largest ethnic group, from the south Fukien coast. They spoke the dialect known variously as Amoy, Minnan, or Hoklo, and they continued to migrate to Taiwan until World War II. The version of their language which is spoken on the island is usually called "Taiwanese"; there are regional variations between northern and southern Taiwan. Between the 14th and 17th centuries, Hoklo emigrants left China despite an imperial decree forbidding overseas travel. The trickle of Chinese immigrants in Taiwan increased rapidly in the 17th and 18th centuries. Often, the Hoklo residents of Taiwan are called "native Taiwanese," though this term is also used to designate anyone whose family arrived in Taiwan before 1949. In recent years, the term "Taiwanese" is increasingly used to mean everyone who lives in Taiwan and identifies primarily with the island. Hoklo people account for the overwhelming majority of the populace, about 70% of the total.

In the 17th century, another group of Han people began migrating to Taiwan, speakers of the Hakka (Ke Chia) dialect from the coastal province of Kwangtung (Canton). Hoklo settlers had already taken most of the best land on the plains, and viewed the new arrivals as intruders. Thus the Hakka moved to poorer land in the foothills, where they often faced hostility from the aborigines. They went about the dangerous and difficult work of developing Taiwan’s forest products industry, especially producing camphor wood and oil. Today about 10-15% of the contemporary population of Taiwan speaks Hakka. While this includes some post-1949 immigrants from mainland China, most Taiwanese Hakka have deep roots on the island.

Throughout the world, Hakka, who are thought to be the descendants of a deposed Chinese imperial dynasty, are known for their industriousness and political skills. Leading Hakka politicians include former Singapore Prime Minister Lee Knan-Yew, and Communist China’s strongman, Teng Hsiao-ping. Taiwan-born President Lee Teng-hui’s ancestry is Hakka on one side.

In Taiwan, the Hakka live mainly in the northwester counties of Taoyuan, Hsinchu, and Miaoli, as well as on the east coast and in southern Pintung County. They account for a disproportionate share of Taiwan’s industrial working class. Recently, however, many Hakka workers have managed to accumulate capital and become successful business owners.

According to government statistics, the remaining 12-15% of the total population consists of immigrants who arrived from mainland China between 1945 and 1949. Although these people are generally referred to as "mainlanders," the majority of them were in fact born on the island. Census procedures employed by the government designate the birth place of the Taiwan-born wives and children of mainland refugees as identical to that of the father. Taking this practice into account would deflate to 3.3% representation of mainlanders in the population. Indeed, over 90% of the people living on Taiwan today were born there. People from virtually all of China’s diverse ethnic, religious, and linguistic groups can be found in Taiwan’s mainlander community, including Hakka and Hoklo (Taiwanese) speakers from Kwangturng and Fukien Provinces.

Mandarin - the Beijing dialect of Chinese - is the official language, but many older people who grew up during the Japanese rule (1895-1945) do not speak it well, preferring to use Taiwanese or Japanese.  On the other hand, Taiwanese is widely spoken in informal settings, and many younger Taiwan-born "mainlanders" have learned Taiwanese or Hakka.