Ramanathi (ராமாநதி) is a river flowing in the Tirunelveli district of the Indian state of Tamil Nadu.Gadananathi originates from Agasthyamalai Biosphere Reserve.This river enters Gadananathi River in Kizha Ambur. The Ramanadhi has 7 anicuts, a reservoir of 4,300,000 cubic metres (3,500 acre·ft), and irrigates 20.23 square kilometres (7.81 sq mi) of wetlands. This river flows on many villages like Alwarkurichi, Ravanasamudram, Pottalpudur, Pillaukulam.The Gadananathi is fed by Thekkaru and Ramanathi Rivers.
Ramanathi reservoir is located at the foot of the Western ghats in Kadayam village of Ambasamudram Taluk in Tirunelveli District. It is one of tourist place in this district. Now a lot of tourists are visiting the dam and park.