About Thamirabarani River - தாமிரபரணி ஆறு in Agastya Mala, Tirunelveli

The Thamirabarani River (Porunai) (Tamil: தாமிரபரணி(பொருனை) is a perennial river that originates from the famous Agastyarkoodam peak of Pothigai hills of the Western Ghats, above Papanasam in the Ambasamudram taluk. It flows through Tirunelveli and Tuticorin districts of the Tamil Nadu state of southern India into the Gulf of Mannar. It was called the Tamraparni River in the pre-classical period, a name it lent to the island of Sri Lanka. The old Tamil name of the river is Porunai. From the source to sea, the river is about 185 kilometres (115 mi) long and is the only perennial river in South India.

Its many name derivations of Tan Porunai include Tampraparani, Tamraparni, Tamiravaruni. Tan Porunai nathi finds mention by classical Tamil poets in ancient Sangam Tamil literature Purananuru. Recognised as a holy river in Sanskrit literature Puranas, Mahabharata and Ramayana, the river was famed in the Early Pandyan Kingdom for its pearl and conch fisheries and trade. The movement of people, including the faithful, trade merchants and toddy tapers from Tamraparni river to NorthWestern Sri Lanka led to the shared appellation of the name for the closely connected region. One important historical document on the river is the treatise Thamirabarani Mahathmiyam. It has many ancient temples along its banks.

In the Mahābhārata (3:88) the river is mentioned as "Listen, O son of Kunti, I shall now describe Tamraparni. In that asylum the gods had undergone penances impelled by the desire of obtaining salvation".