Nagar River (Bengali : ন গ র নদী) is in the Bogra District of Bangladesh:
The Nagar is a branch of the Karatoya and serves as the boundary between the Sibganj and Bogra thanas, for about seven miles. It then passes between the former ana the Dhup chanchia thana and then Adamdighi down to the village of Champapur. It then turns off west wards and passing through the Dupchanchia thana enters Rajshahi district. It falls in the Atrai, near the Singra thana in the Rajshahi district. It is a tortuous river, and its whole length in this district, including the windings is about 30 miles. On its banks are situated the important villges of Elahiganj and Dhupchanchia. It is navigable by boats only during the rainy season.