The Thamirabarani River originates from the famous Agastyarkoodam peak of Pothigai hills of the Western Ghats, above Papanasam in the Ambasamudram taluk. It flows through Tirunelveli and Thoothukudi 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 125 kilometres long.