The Vaigai River flows in the southern part of India. The historic city of Madurai in Tamil Nadu is situated on the banks of this river. The river flows for 150 miles (240 kilometres) generally in the southeast direction and rarely causes floods. The Vaigai River basin in Tamil Nadu covers an area of 7,000 square kilometers.

The river rises in the Periyar plateau of the Western Ghats. It then flows in the northeast direction through the Kambam Valley. The Kambam Valley lies between the Palni Hills to the north and the Varushanad Hills in the south. From the Varushanad Hills, the river turns in the southeast direction and flows through the Pandya Nadu region. Madurai is the largest city of this region and is situated on the banks of the Vaigai River. The river finally evacuates in to the Palk Strait, a 64-137 km wide channel in Ramanathapuram district.

The major tributaries of the Vaigai River are Suruliyaru, Mullaiyaaru, Varaganadi and Manajalaru. The tributaries merge with the Vaigai River at places near the Vaigai Dam. The Vaigai Dam is built across the Vaigai River and is situated in Theni district.