King Anawrahta (A.D. 1044-1077), also spelled ANIRUDDHA, the first king of all of Myanmar, (reigned 1044-77), who introduced his people to Theravada Buddhism. His capital at Bagan on the Ayeyarwaddy River became a prominent city of pagodas and temples. During his reign Anawrahta united the northern homeland of the Myanmar people with the Mon kingdoms of the south.
He extended his dominion as far north as the kingdom of Nanchao, west to Arakan, south to the Gulf of Martaban (near what is now Yangôn), and as far east as what is now northern Thailand.
In 1057 Anawrahta captured the Mon city of Thaton, a centre of Indian civilization. Its fall led the other Mon rulers to submit to Anawrahta; for the first time, a Myanmar ruler dominated the Ayeyarwaddy River delta. Contact with the Mons enriched Myanmar civilization. The Mons gave the Myanmar an artistic and literary tradition and a system of writing. The earliest extant Myanmar inscription, written in Mon characters, appeared in 1058.
Anawrahta was converted to Theravada Buddhism by a Mon monk, Shin Arahan. As king, Anawrahta strove to convert his people from the influence of the Ari, a Mahayana Tantric Buddhist sect that was at that time predominant in central Myanmar. Primarily through his efforts, Theravada Buddhism became the dominant religion of Myanmar and the inspiration for its culture and civilization. He maintained diplomatic relations with King Vijayabahu of Ceylon, who in 1071 requested the assistance of Myanmar monks to help revive the Buddhist faith. The Ceylonese king sent Anawrahta a replica of the Buddha's tooth relic, which was placed in the Shwezigon pagoda at Pagan.