Gundar River flows through Madurai, Virudhunagar and Ramanathapuram districts of the Indian state of Tamil Nadu. The origin of Gundar is Sathuragiri hills, and it flows through Tirumangalam, Kamuthi and ends itself into Gulf of Mannar.
References http://www.nellai.tn.nic.in/general.html#rivers
See also List of rivers of Tamil Nadu