Manimuthar River originates on the eastern slopes of Western Ghats in Tirunelveli District of the state of Tamil Nadu in southern India. It is a major tributary of the Tambaraparani River. The river begins in the dense forest on a mountain peak above sea level in Ambasamudram taluk and flows though small cataracts until it reaches the Tambaraparani River near Kallidaikurichi. The tributaries of the Manimuthar are the Keezha River and the Varattar River. As a tributary, the Manimuther River adds a considerable amount of water to the Tamiraparani River as it seasonally is always in full. In 1957, Manimuthar anicut was built across the river before its juncture with the Tamiraparani.