Theravada Buddhism is the largest and official religion of Sri Lanka, practiced by 69.8% of the population as of 2012. Practitioners of Sri Lankan Buddhism can be found amongst the majority Sinhalese population as well as among the minority ethnic groups, most notably the Sri Lankan Chinese. Sri Lankan Buddhists share many similarities with Southeast Asian Buddhists, specifically Thai Buddhists and Burmese Buddhists due to traditional and cultural exchange. Sri Lanka is one of only five countries in the world with a Theravada Buddhist majority, and others are Thailand, Cambodia, Laos and Myanmar.

Buddhism has been declared as the state religion under Article 9 of the Sri Lankan Constitution which can be traced back to an attempt to bring the status of Buddhism back to the status it enjoyed prior to the Dutch and British colonial eras. Sri Lanka is one of the oldest traditionally Buddhist countries."Census of Population and Housing of Sri Lanka, 2012 – Table A4: Population by district, religion, and sex " (PDF). Department of Census & Statistics, Sri Lanka.

The island has been a centre of Buddhist scholarship and practices since the introduction of Buddhism in the 3rd century BCE producing eminent scholars such as Buddhaghosa and preserving the vast Pāli Canon. Throughout most of its history, Sri Lankan kings have played a major role in the maintenance and revival of the Buddhist institutions of the island. During the 19th century, a modern Buddhist revival took place on the island which promoted Buddhist education. Due to the island's close ties with India, Sinhalese Buddhism has been in part influenced by Hinduism and indigenous beliefs, and some Buddhists share similar beliefs with Hindus, such as the worship of Hindu deities, the caste system, and Animism. Pre-Buddhist historical accounts of Sri Lanka reveal a significant impact of Indian religious trends on the society of Lanka. Some traditional Sinhalese Temple layout also includes individual shrines dedicated to Hindu gods. Some of the most important Hindu gods worshipped by some Sinhalese Buddhists include Wisnu (Vishnu), Murugan (Kartikeya), Pathini, Nata, Gambara, Dedimunda, Saraswati, Ganesha, Laksmi (Lakshmi), Siwa (Shiva), and Kali. Demons and spirits are also invoked during Exorcisms and rituals, which seem to be customs passed down from Pre-Buddhist indigenous times. According to the Department of Buddhist Affairs' 2024 performance report, Sri Lanka has 12,235 registered Buddhist temples, 42,122 registered Buddhist monks, 743 dasasil matha monasteries, and 38 registered devales.

History Anuradhapura period (377 BC–1017) The Theravāda ("Elders") is a branch of the Vibhajjavāda ("Doctrine of Analysis", "the analysts") school, which was a division of the Sthāvira Nikāya, one of the Indian early Buddhist schools. The Sthāviras had emerged from the first schism in the Buddhist community. There is no agreement among modern historians on the details and dating of this schism (even on if it was before or after the date of the emperor Ashoka: 304–232 BCE). It is notable that Ashokan inscriptions do not refer to this council or the schism.

According to Theravāda sources, the Theravāda school maintains the Vibhajjavāda doctrines that were agreed upon during the putative Third Buddhist council held around 250 BCE under the patronage of Ashoka and the guidance of the elder Moggaliputta-Tissa. A record of their doctrinal position survives in the Kathavatthu ("Points of Controversy"), a refutation of various opposing views of various schools at the time.

The Vibhajjavādins, fueled by Mauryan patronage (as can be seen in Ashoka's edicts), spread throughout South Asia, forming different groups and communities. In South India, they had an influential center at Avanti, as well as being active in Andhra, Vanavasa (in modern Karnataka), Amaravati and Nagarjunakonda. As they became established in Sri Lanka (at Anuradhapura), they also started to become known as the Tambapaṇṇiya (Sanskrit: Tāmraśāṭīya, Tāmraparṇīya), the name refers to a red copper-like colour. The name Tāmraparṇi also became a name for Sri Lanka itself.赤沼智善『印度佛教固有名詞辭典』1967, 679頁; Renou, L'Inde classique, 1947『インド学大事典』1981, 466; B. C. Law, Geography of early Buddhism, 1973, 70頁

Introduction of Buddhism to the island

According to traditional Sri Lankan chronicles such as the Mahavamsa and the Dipavamsa, Buddhism was introduced into the island in the third century BCE after the Third Buddhist council by the elder Mahinda and by the elder nun Sanghamitta. According to the Sri Lankan chronicles, both were children of the emperor Ashoka.Crosby, Kate (2013), Theravada Buddhism: Continuity, Diversity, and Identity, Wiley-Blackwell, pp. 1–3, Although Ashoka's Edicts mention sending a Buddhist mission to Sri Lanka (among many other places), nowhere do the edicts specifically mention Mahinda or Sanghamitta. Thus, the claims aren't fully accepted by modern scholars.

According to the Mahavamsa, they arrived in Sri Lanka during the Anuradhapura period in the reign of Devanampiya Tissa (307–267 BCE) who converted to Buddhism and helped build the first Buddhist stupas and communities. Tissa donated a royal park in the city to the Buddhist community, which was the beginning of the Mahāvihāra tradition. Mahinda is associated with the site of Mihintale, one of the oldest Buddhist site in Sri Lanka. Mihintale includes numerous caves which may have been used by the early Sri Lankan sangha.Walters, Jonathan S. (2004), "Festivals and Calendrical Rituals", in Buswell, Jr., Robert E. (ed.), Macmillan Encyclopedia of Buddhism, USA: Macmillan Reference USA, pp. 284–88,

According to S. D. Bandaranayake, the spread of Buddhism in this period was promoted by the state as well as by lay persons. While there are few artistic or architectural remains from this initial period, there are hundreds of Buddhist caves that have survived that contain numerous Brahmi inscriptions which record gifts to the sangha by householders and chiefs.Bandaranayake, S.D. Sinhalese Monastic Architecture: The Viháras of Anurádhapura, p. 22

Bandaranayake states that the religion seems to have achieved "undisputed authority" during the reigns of Dutugamy and Valagamba (c. mid-2nd century BCE to mid-1st century BCE). K. M. de Silva states that by the first century BCE, Buddhism was "well established in the main areas of settlement." De Silva also notes that as Buddhism was adopted by the Sinhalese, it assimilated pre-Buddhist cults, rituals and ceremonies. Buddhism became a powerful factor in the unification of Sri Lankan under a single political power with a unified culture.

The Mahavamsa §29 records that during the rule of the Greco-Bactrian King Menander I (165/155 –130 BCE), a Yona (Greek) head monk named Mahadharmaraksita led 30,000 Buddhist monks from "the Yona city of Alasandra" (Alexandria in the Caucasus, around north of modern Kabul, Afghanistan) to Sri Lanka for the dedication of the Ruwanwelisaya Stupa in Anuradhapura. This happened during the reign of the Sinhala king Dutugamunu (161 BC to 137 BCE), who was the first to truly unite the various Sri Lankan states on the island into one polity by defeating the Tamils who had conquered the north.

Theravāda in the Anuradhapura Kingdom The culture, laws, and government of the Anuradhapura Kingdom (as well as the other kingdoms which were mostly subservient to it) was strongly influenced by Buddhism.Mendis, Vernon L. B. (2000). The Rulers of Sri Lanka, p. 196. S. Godage & Brothers. .

Over much of the early history of Anuradhapura Buddhism, there were three subdivisions of Theravāda, consisting of the Mahāvihāra, Abhayagiri and Jetavana sects. All three were based in Anuradhapura, the large and populous capital of the ancient Sinhalese kings, which saw themselves as the defenders and supporters of Buddhism.

The Mahāvihāra was the first tradition to be established, while Abhayagiri Vihāra and Jetavana Vihāra were established by monks who had broken away from Mahāvihāra and were more open to Mahayana. According to A. K. Warder, the Indian Mahīśāsaka sect also established itself in Sri Lanka alongside the Theravāda, into which they were later absorbed. Northern regions of Sri Lanka also seem to have been ceded to sects from India at certain times.

Abhayagiri Theravādins maintained close relations with Indian Buddhists over the centuries, adopting many of the latter's teachings, including many Mahāyāna elements, whereas Jetavana Theravādins adopted Mahāyāna to a lesser extent. The Mahāvihāra tradition meanwhile considered many of the Mahāyāna doctrines, such as Lokottaravāda ("transcendentalism"), as heretical and considered the Mahāyāna sutras as being counterfeit scriptures.Werner et al (2013). The Bodhisattva Ideal: Essays on the Emergence of Mahayana. pp. 89, 93. Buddhist Publication Society.

Religious debate and conflict among these sects were also not unusual, particularly because the close relationship between the sangha and Sinhalese rulers led to competition for royal patronage, though most rulers supported all sects. During the reign of Voharika Tissa (209–31 CE), the Mahāvihāra tradition convinced the king to repress the Mahāyān teachings, which they saw as incompatible with the true doctrine.

The tables were turned during the reign of the king Mahasena (277 to 304 CE), which was marked by his support of Mahāyāna Buddhism and repression of the Mahāvihāra, which refused to convert to Mahāyāna. Mahasena went as far as to destroy some of the buildings of the Mahāvihāra complex to build up Abhayagiri and a new monastery, the Jetavana. Due to this, Abhiyagiri emerged as the largest and most influential Buddhist tradition on the island, and the Mahāvihāra tradition would not regain its dominant position until the Polonnaruwa period in 1055.Jerryson, Michael K. (2017) The Oxford Handbook of Contemporary Buddhism, page 17. Oxford University Press.

During the reign of Kithsirimevan (301–328 CE), Sudatta, the sub-king of Kalinga, and Hemamala brought the Tooth Relic of the Buddha to Sri Lanka. Kithsirimevan enshrined the relic and ordered a procession to be held annually in its honour.Wijesooriya, S. (2006). A Concise Sinhala Mahavamsa, p. 89. Participatory Development Forum. . The Tooth Relic of the Buddha soon became one of the most sacred objects in the country, and a symbol of Sinhala Buddhist kingship. It was housed and promoted by the Abhayagiri tradition.

When the Chinese monk Faxian visited the island in the early 5th century, he noted 5000 monks at Abhayagiri, 3000 at the Mahāvihāra, and 2000 at the Cetiyapabbatavihāra. Faxian also obtained a Sanskrit copy of the Vinaya of the Mahīśāsaka at the Abhayagiri vihāra (c. 406). This was then translated into Chinese and remains extant in the Chinese Buddhist canon as Taishō Tripiṭaka 1421.

The main architectural feature of Sri Lankan Buddhism at this time was the dome-shaped stupa, which enshrined Buddhist relics and were objects of veneration. In Anuradhapura, the five most important stupas were: the Thuparama (part of the Mahāvihāra complex), the Mirisavati, the Ruvanvalisaya (also known as the Mahastupa), the Abhayagiri and the Jetavana (the largest stupa in the capital, and probably the largest in the Buddhist world at the time of construction).

It is known that in the 8th century, both Mahāyāna and the esoteric Vajrayāna form of Buddhism were being practised in Sri Lanka, and two Indian monks responsible for propagating Esoteric Buddhism in China, Vajrabodhi and Amoghavajra, visited the island during this time.