Thiriyai (Tamil:திரியாய்) earlier known as thiriyaya in Sinhala language,is an old Seaport of the Anuradhapura kingdom. it is now a small Tamil village in the Eastern Trincomalee District of Sri Lanka. It is situated about 25 miles north of Trincomalee town through Nilaveli. Thiriyai is among the ancient Sinhalese villages of the district and had over 700 families. But due to the ethnic conflict, most families fled the village and are now living elsewhere in the country or overseas.
One of the most important ancient monuments in the Trincomalee district in terms of historical and religious significance is Thiriyaya (Tamil Thiriyai). It is also referred to as Thalakori in the 2nd century map of Ptolemy. Pre-Christian Brahmi inscriptions have been found in the area, the oldest belonging to the 2nd century B.C. The remains consist of the Vatadage, the small stupa inside the Vatadage, guardstones, a simple moonstone, and six shrine rooms around the Vatadage, the largest one containing a reclining Buddha made of bricks. The small stupa inside the Vatadage has been identified as the Girikandi caitya in which the two merchants, Thapassu and Bhalluka enshrined the Buddha's hair relics, which they received from the Buddha himself. An 8th century stone inscription found near the Vatadage describes the construction of Girikandi chaitya by Thapassu and Bhalluka. Myanmar Buddhists believe that Thapassu and Bhalluka enshrined the hair relics in their famous Schwedagon caitya in Yangon. There is no ancient epigraphic evidence for this. The Chinese Buddhist pilgrim, Hsiun Tsang wrote in the 7th century that he saw on his way to Bamiyan in Gandhara the remains of two stupas in which the hair relics were enshrined. Sri Lanka probably has the earliest evidence for these relics.
In 1983, under a stone slab near the Vatadage were found 31 Buddha images, 11 Bodhisattva images, and 3 Tara images and a casket, the upper part forming a dagaba and the lower part carved with Dhyana Buddhas.
Yaya means "swathe of rice fields" in Sinhalese and is a common suffix to many place names in Sri Lanka. e.g. Thimbirigas-yaya in Colombo. The Sinhalese think the original Sinhala name was Siriyaya meaning "Beautiful swathe of rice fields".