Mayurakshi River (also called Mor River) is a major river in Jharkhand and West Bengal, India, with a long history of devastating floods. It has its source on Trikut hill, about 16 kilometres (10 mi) from Deoghar in Jharkhand state. It flows through Jharkhand and then through the districts of Birbhum and Murshidabad in West Bengal before flowing into the Hooghly River. The river is about 250 kilometres (160 mi) long.

Mayurakshi literally means "peacock eyes" (mayur/mor=peacock, akshi=eye). The comparison is with the beautiful feathers on a peacock's tail. Mayurakshi though named after its crystal clear water of the dry seasons, floods its valley during the monsoons. Even after the construction of the Massanjore dam, it wreaks havoc with its floods, washing away embankments.