The earliest established religions in Vietnam are Mahayana Buddhism, Confucianism, and Daoism (called the triple religion or tam giao). Significant minorities of adherents to Roman Catholicism, Cao Dai, and Hoa Hao and smaller minorities of adherents to Protestantism, Islam, Brahmanism, and Theravada Buddhism were established later, in recent centuries.
The majority of Vietnamese people classify themselves as non-religious, although they visit religious temples several times every year. Their everyday behaviours and attitudes are dictated by the synthesis of philosophies which can be traced from many religions, especially Mahayana Buddhism, Confucianism, and Daoism. Those religions have been co-existing in the country for centuries and mixed perfectly with the Vietnamese tradition of worshiping their ancestors and national heroes. That special mix explains why the people there find it hard to say exactly which religion they belong to.
Of Vietnam’s many religions, Buddhism is the most popular (92% of Vietnam’s population is Buddhist).There are two types of Buddhism found in Vietnam, Mahayana Buddhism and Theravada. Mahayana Buddhism first spread from China to Vietnam’s Red River Delta region around 300 BC and remains popularly followed throughout the whole country, whereas Theravada Buddhism arrived from India into the southern Mekong Delta region between 300-600 AD and remains commonly adhered to in only the south delta area of Vietnam. To this day, Mahayana Buddhism is largely affiliated with the majority ethnic Vietnamese.
As communism began to rise in Vietnam, the regime generally avoided going against Buddhism but began to actively suppress any other religion. Instead, they declared that all Buddhists supported the new communist regime, in order to reduce the power of influential Buddhists that did not encourage communism, such as the United Buddhist Church of Vietnam. The Communist government also forced nuns and monks to live a materialistic life as well as to work in agricultural labor and join the Patriotic Buddhist Liaison Committee. If they refused, they were placed under house arrest or imprisoned, and their pagodas and possessions were taken for public use. The government also prohibited Buddhist organizations from creating schools to train new monks and nuns. By April 1980, most of the Buddhist organizations were fully controlled by the government. Because of this, Buddhist rituals and practices relatively decreased and most pagodas were eliminated.
Cao Dai and Hoa Hao are minority religions in Vietnam that were both founded in the Mekong River Delta during the 19th century. Cao Dai is a type of reformed Buddhism with principles taken from Confucianism, Taoism, and Christianity that became popular in the rural regions of the southern delta area whereas Hao Hao is related closer to tradition Buddhism and became popular in the southernmost areas of the delta.
As the communist regime fought for power, most of the Cao Dai and Hao Hao organizations tried to remain neutral throughout the conflict. However, by 1975, the Communist government (as they did to the Roman Catholics and Buddhists) began to pressure all Cao Dai and Hao Hao organizations to join the Communist cause.