The main religion in Tibet has been Buddhism since its outspread in the 8th century AD. The historical region of Tibet (the areas inhabited by ethnic Tibetans) is nowadays mostly comprised by the Tibet Autonomous Region of China, and partly by the provinces of Qinghai and Sichuan. Before the arrival of Buddhism, the main religion among Tibetans was an indigenous shamanic and animistic religion, Bon, which now comprises a sizeable minority and which would later influence the formation of Tibetan Buddhism.
According to estimates from the International Religious Freedom Report of 2012, most of Tibetans (who comprise 91% of the population of the Tibet Autonomous Region) are bound by Tibetan Buddhism, while a minority of 400,000 people (12.5% of the total population of the TAR) are bound to the native Bon or folk religions which share the image of Confucius (Tibetan: Kongtse Trulgyi Gyalpo) with Chinese religion, though in a different light. According to some reports, the government of China has been promoting the Bon religion linking it with Confucianism.
There are four mosques in the Tibet Autonomous Region with approximately 4,000 to 5,000 Muslim adherents, although a 2010 Chinese survey found a higher proportion of 0.4%. There is a Catholic church with 700 parishioners, which is located in the traditionally Catholic community of Yanjing in the east of the region.
Religion is extremely important to the Tibetans and has a strong influence over all aspects of their lives. Bön is the ancient religion of Tibet, but nowadays the major influence is Tibetan Buddhism, a distinctive form of Mahayana and Vajrayana, which was introduced into Tibet from the Sanskrit Buddhist tradition of northern India. Tibetan Buddhism is practiced not only in Tibet but also in Mongolia, parts of northern India, the Buryat Republic, the Tuva Republic, and in the Republic of Kalmykia and some other parts of China. During China's Cultural Revolution, nearly all Tibet's monasteries were ransacked and destroyed by the Red Guards. A few monasteries have begun to rebuild since the 1980s (with limited support from the Chinese government) and greater religious freedom has been granted - although it is still limited. Monks returned to monasteries across Tibet and monastic education resumed even though the number of monks imposed is strictly limited. Before the 1950s, between 10 and 20% of males in Tibet were monks.
Tibetan Buddhism has four main traditions (the suffix pa is comparable to "er" in English):
Bön, the indigenous animist and shamanic belief system of Tibet, revolves around the worship of nature and predates Buddhism. Although Bön was initially the religion to which Buddhas teachings were antithetical, it now has been recognised as a legitimate religion by the 14th Dalai Lama.
According to Bon religious texts: three Bon scriptures--mdo 'dus, gzer mig, and gzi brjid--relate the mythos of Tonpa Shenrab Miwoche. The Bonpos regard the first two as gter ma rediscovered around the eleventh century and the last as nyan brgyud (oral transmission) dictated by Loden Nyingpo, who lived in the fourteenth century. In the fourteenth century, Loden Nyingpo revealed a terma known as The Brilliance (Wylie: gzi brjid), which contained the story of Tonpa Shenrab. He was not the first Bonpo tertön, but his terma became one of the definitive scriptures of Bon religion. It states that Shenrab established the Bon religion while searching for a horse stolen by a demon. Tradition also tells that he was born in the land of Tagzig Olmo Lung Ring (considered an axis mundi) which is traditionally identified as Mount Yung-drung Gu-tzeg ("Edifice of Nine Sauwastikas"), possibly Mount Kailash, in western Tibet. Due to the sacredness of Tagzig Olmo Lungting and Mount Kailash, the Bonpo regard both the swastika and the number nine as auspicious and as of great significance.
Tonpa Shenrab Miwoche visited Kongpo and found people whose practice involved spiritual appeasement with animal sacrifice. He taught them to substitute offerings with symbolic animal forms made from barley flour. He only taught according to the student's capability with lower shamanic vehicles to prepare; until with prayer, diligence, devotion and application they could incarnate to achieve sutra, tantra and Dzogchen.
Bon teachings feature Nine Vehicles, which are pathway-teaching categories with distinct characteristics, views, practices and results. Medicine, astrology, and divination are in the lower vehicles; then sutra and tantra, with Dzogchen great perfection being the highest. Traditionally, the Nine Vehicles are taught in three versions: as Central, Northern and Southern treasures. The Central treasure is closest to Nyingma Nine Y?nas teaching and the Northern treasure is lost. Tenzin Wangyal Rinpoche elaborated the Southern treasure with shamanism.
Most of the Han Chinese who reside in Tibet practice their native Chinese folk religion (Shendao , "Way of the Gods"). There is a Guandi Temple of Lhasa () where the Chinese god of war Guandi is identified with the cross-ethnic Chinese, Tibetan, Mongol and Manchu deity Gesar. The temple is built according to both Chinese and Tibetan architecture. It was first erected in 1792 under the Qing dynasty and renovated around 2013 after decades of disrepair.
There is a Tibetan folk religious sect in Amdo County named the "Heroes of Ling", which was founded in 1981 by a Tibetan called Sonam Phuntsog, who claimed to be an incarnation of the legendary hero Gesar. At its peak in the 1980s the movement had attracted converts among local communist leaders. It was later banned as a disruptive and "splittist" sect.
The first Christians documented to have reached Tibet were the Nestorians, of whom various remains and inscriptions have been found in Tibet. They were also present at the imperial camp of Möngke Khan at Shira Ordo, where they debated in 1256 with Karma Pakshi (1204/6-83), head of the Karma Kagyu order. Desideri, who reached Lhasa in 1716, encountered Armenian and Russian merchants.
Roman Catholic Jesuits and Capuchins arrived from Europe in the 17th and 18th centuries. Portuguese missionaries Jesuit Father António de Andrade and Brother Manuel Marques first reached the kingdom of Gelu in western Tibet in 1624 and was welcomed by the royal family who allowed them to build a church later on. By 1627, there were about a hundred local converts in the Guge kingdom. Later on, Christianity was introduced to Rudok, Ladakh and Tsang and was welcomed by the ruler of the Tsang kingdom, where Andrade and his fellows established a Jesuit outpost at Shigatse in 1626.
In 1661 another Jesuit, Johann Grueber, crossed Tibet from Sining to Lhasa (where he spent a month), before heading on to Nepal. He was followed by others who actually built a church in Lhasa. These included the Jesuit Father Ippolito Desideri, 1716-1721, who gained a deep knowledge of Tibetan culture, language and Buddhism, and various Capuchins in 1707-1711, 1716-1733 and 1741-1745, Christianity was used by some Tibetan monarchs and their courts and the Karmapa sect lamas to counterbalance the influence of the Gelugpa sect in the 17th century until in 1745 when all the missionaries were expelled at the lama's insistence.
In 1877, the Protestant James Cameron from the China Inland Mission walked from Chongqing to Batang in Garzê Tibetan Autonomous Prefecture, Sichuan province, and "brought the Gospel to the Tibetan people."
During the 1905 Tibetan Rebellion Tibetan Buddhist lamas attacked, tortured and killed French Catholic missionaries and killed Tibetans who converted to Catholicism. In 1949 Tibetan lamas killed Fr Maurice Tornay.
Muslims have been living in Tibet since as early as the 8th or 9th century. In Tibetan cities, there are small communities of Muslims known as Kachee (Kache), who trace their origin to immigrants from three main regions: Kashmir (Kachee Yul in ancient Tibetan), Ladakh and the Central Asian Turkic countries. Islamic influence in Tibet also came from Persia. After 1959 a group of Tibetan Muslims made a case for Indian nationality based on their historic roots to Kashmir and the Indian government declared all Tibetan Muslims Indian citizens later on that year. Other Muslim ethnic groups who have long inhabited Tibet include Hui, Salar, Dongxiang and Bonan. There is also a well established Chinese Muslim community (gya kachee), which traces its ancestry back to the Hui ethnic group of China. The Balti Tibetans of Baltistan are Shia Muslims.
Religion in Tibet is regulated by the laws of the People's Republic of China, which prohibits religions or use of religions for disrupting social harmony. Buddhist leaders such as Gedhun Choekyi Nyima and Tenzin Deleg remain in detention or prison.