The Vaigai is a river in the Tamil Nadu state of southern India; it passes through the towns of Theni, Madurai and Ramanathapuram.

As it rounds the eastern corner of the Varushanad Hills, the river turns southeast, running through the region of Pandya Nadu.

Madurai, the largest city in the Pandya Nadu region and its ancient capital, lies on the Vaigai.

Sangam literature (circa 300 BCE to 300 CE[4][5][6]) has paid many tributes to Vaigai, extolling it as 'the river that brings water when one touches it', viz the etymology Vai (Earth) + yai (sky) = Vaiyai.

It is believed that Vishnu stood up as Trivikrama, with one of his feet rising to the skies and the foot reached Brahmaloka, the abode of Brahma.

Brahma was pleased to perform ablution to the raised foot and the water is believed to have emerged as a rivulet called Krithimala.

[14] The Mullaperiyar Dam was built in 1895 by John Pennycuick, who implemented a plan proposed over a century earlier by Pradani Muthirulappa Pillai of Ramnad.