The southern route in outline
The southern transmission refers to the movement of Buddhism from India south to Sri Lanka and from there, and through other contacts, to Southeast Asia. It is usually contrasted with the northern route through Central Asia. The labels are conveniences: in practice, Southeast Asia received influences from Sri Lanka, from southern and eastern India, and from China, by both land and sea. Dates are approximate and mix tradition with archaeology.
Sri Lanka
According to the Sri Lankan chronicles, Buddhism reached the island in the 3rd century BCE during the reign of King Devanampiya Tissa, brought by the monk Mahinda, who is traditionally said to have been sent by the Mauryan ruler Ashoka. The place linked to his meeting with the king is Mihintale, near Anuradhapura. A nun, Sanghamitta, is said to have brought a branch of the Bodhi tree, and the Sri Maha Bodhi tree is traditionally believed to descend from it. The chronicles were written down centuries later, and the details are treated cautiously, but the island’s long Buddhist history is well documented from archaeology and inscriptions.
Over the following centuries Sri Lanka became a centre of Pali learning. Tradition says the Pali texts were written down there in the 1st century BCE, and commentaries were produced. Monastic communities sometimes divided over disputes, and kings supported or reformed the sangha at different times, with Anuradhapura and later Polonnaruwa serving as capitals and Buddhist centres. Sri Lankan Buddhism has also had periods of decline and revival, including under colonial rule. Monks from Sri Lanka helped re-establish ordination lines in several Southeast Asian countries in later centuries.
Mainland Southeast Asia
The early history of mainland Southeast Asia is less clear. From around the early centuries CE, Indian traders and religious ideas reached the coasts and river valleys. Early states received Buddhism alongside Hindu traditions, and different forms co-existed: archaeology finds Theravada, Mahayana and, later, tantric imagery in various places.
- Myanmar. Buddhist communities such as the Pyu kingdoms are known from the early first millennium CE. Later, the Bagan kingdom (roughly 11th to 13th centuries) built thousands of temples and is linked with the adoption of Theravada, with monks and texts from the Mon and from Sri Lanka playing roles. The Shwedagon Pagoda and Shwezigon Pagoda belong to the later devotional landscape.
- Thailand. Early Mon centres such as Dvaravati had Buddhist art. Over time the Thai kingdoms, including Sukhothai and Ayutthaya, supported Sri Lankan-style Theravada. The modern monastic structure was shaped by royal reforms in the 19th century.
- Cambodia. Khmer rulers supported Hindu and Mahayana Buddhist cults, as at Angkor, with Angkor Wat Hindu to Buddhist change over time. Theravada became dominant in the later medieval period. The twentieth-century violence and its aftermath badly disrupted the sangha, and in recent decades has seen a Khmer Theravada revival.
- Laos. Theravada was established under the Lan Xang kingdom from the 14th century, though earlier Buddhist influences existed.
Island Southeast Asia
In the Indonesian archipelago, Buddhism and Hinduism flourished side by side in kingdoms such as Srivijaya, which was a Buddhist learning centre mentioned by Chinese pilgrims, and the Sailendra dynasty of central Java, associated with Borobudur in the 8th and 9th centuries CE. Later, Islam became the majority religion in much of the region, and Buddhist communities there are now small, though Borobudur remains an important heritage site and a place for Buddhist ceremonies.
Why Theravada became dominant on the mainland
Several factors are commonly discussed: royal support for Sri Lankan-linked orders, which gave rulers a model of a purified sangha; the appeal of a clear monastic code; and the movement of monks between Sri Lanka, Myanmar, Thailand, Cambodia and Laos. Historians stress that this was gradual, uneven and regionally varied, and that older practices persisted alongside Theravada. The picture of Theravada Southeast Asia as a unified bloc is itself a modern simplification.
For visitors
The result of this history is a rich mix. In temples one may see Sri Lankan-style stupas, Burmese pagodas, Khmer towers and Javanese stepped monuments. Customs such as dress, offerings and conduct around monks vary by country. Check current official sources for access and local rules.