Ajay River is a river which flows through the Indian states of Bihar, Jharkhand and West Bengal.Ajay River originates on a small hill about high, southwest of Deoghar in Jharkhand. It then flows through Jharkhand and enters West Bengal at Simjuri. It enters Katwa subdivision of Bardhaman district at Nareng village.It then joins the Bhagirathi River at Katwa Town. Total length of the Ajay is , out of which are in West Bengal. The important tributaries of the Ajay are Pathro and Jayanti in Jharkhand, and Tumuni and Kunur in Bardhaman district of West Bengal. The Ajay valley was densely forested with sal, piyasal and palas trees. But in recent times due to mining and other activities the forests were cleared. There have been at least 14 recorded floods in the 20th century caused by the Ajay river.