Religion in Taiwan is characterised by a diversity of religious beliefs and practices, predominantly those pertaining to the continued preservation of ancient Chinese culture and religion. Freedom of religion is enshrined in the constitution of the Republic of China (Taiwan). The majority of Taiwanese people practice a combination of Buddhism and Taoism often with a Confucian worldview, which is collectively termed as Chinese folk religion.

Many statistical analyses try to distinguish between Buddhism and Taoism in Taiwan, which, along with Confucianism, are rather aspects within broader "ancient Chinese religion". It is hard to make such distinction because various Taoist deities are worshipped alongside deities which originated in Buddhism, for instance Guanyin, in many temples across the country.

As of 2024^[update], there were 15,206 temples and churches in Taiwan, including 9,794 Taoist and 2,273 Buddhist temples as well as 2,374 Protestant and 418 Catholic churches. In Taiwan's 36,000 square kilometers of land, there are more than 33,000 places for religious (believers) to worship and gather. Averaging almost one religious building (temple, church, etc.) for every square kilometer, Taiwan is considered to have the highest density of religious buildings, making it the "most religious" region in the area where Chinese is the majority language.

Before the 17th century, the island of Taiwan was inhabited by indigenous peoples of Austronesian origin, as well as small settlements of Chinese and Japanese maritime traders and pirates. Taiwanese indigenous peoples traditionally practised animism. When the Dutch occupied parts of southern Taiwan in 1624, Dutch missionaries soon followed, introducing Protestantism to the indigenous communities. Following the arrival of the Spaniards in northern Taiwan two years later, Catholic missionaries from Spain also came to share their faith.

When the Han Chinese began to settle on the island and form the Taiwanese Chinese ethnic group, interfaith exchanges occurred, leading to two-way religious assimilation between the indigenous and Han communities. An example was the incorporation of Ali-zu, the Siraya god of fertility, into the Han pantheon of folk deities in some places around Taiwan.

A large influx of Han Chinese began in the 1660s with the transition of imperial power from the Ming dynasty to the Manchurian Qing dynasty. Many Ming loyalists fled to the south, including Zheng Chenggong alias Koxinga, a military warlord who fought against the Manchu dynasty. He sailed to Taiwan in 1661 with thousands of troops, and in a war with the Dutch, he defeated and drove out the Dutch military forces and established the Kingdom of Tungning, the first Chinese state on the island. Chinese settlers, mostly from Fujian and Guangdong, began to migrate to the island. The policy of migration to Taiwan was restrictive until 1788, even after the island came under the political control of the Qing in 1683.

Chinese migrants brought with them the Chinese traditional religions from their hometown, which served to integrate communities around the worship of Chinese Deities. As the settlers were mostly males, came from different areas, and at first not many people shared the same surnames and belonged to the same kins, ancestral shrines of kinship gods did not develop until the 1790s, when sufficient generations of families had established on the island.

The first settlers in Koxinga and Qing periods brought with them images or incense ashes from mainland temples, installed them in homes or temporary thatched huts, and later in proper temples, as economic circumstances permitted to build them. Prominent temples became the foci of religious, political and social life, often eclipsing Qing officials and state-sponsored temples in their influence.