The Mithi River is also known as the Mahim River and is located in Salsette Island on which the Mumbai city is situated. The river is actually the merging of the tail water that is discharged from the Powai and Vihar lakes. It is a seasonal river, which feeds on the monsoons.

The river rises from the valley near the Sanjay Gandhi National Park at Powai and merges with the Arabian Sea at Mahim Creek. During its course, the river flows through residential and industrial complexes of Powai, Saki Naka, Kurla, Kalina, Vakola, Bandra-Kurla complex, Dharavi and Mahim for fifteen kilometers. The river is narrow in its initial course, which is nearly ten metres in width, but it widens gradually and is wide at the Bandra Kurla complex. The river is fourteen kilometers in length.

The Mahim bay area where the Mithi River merges with the Arabian Sea is a bird sanctuary, which is called Salim Ali Bird Sanctuary. Many migratory birds visit the area. A dam has been constructed across this river along the upstream side of Vihar Lake. The river is a natural drainage channel, which carries the surplus waters during the monsoon.