Kishanganj district is one of the thirty-eight districts of Bihar state, India, and Kishanganj town is the administrative headquarters of this district. Kishanganj district is a part of Purnia division.

Kishanganj was the old and important Sub-Division of Purnia district. After the long and hard struggle of Seventeen Years from people of Kishanganj including Social Workers, politicians, journalist, businessman’s, Farmers etc., the Kishanganj District came into existence on 14 January 1990.

Since centuries Kishanganj/Darjeeling was part of Nepal and was called Nepalgarh. When on the instructions of the Mughal emperor, Mohammed Reza captured the fort at Nepalgarh, the name was changed to Alamganj. It later became Kishanganj.

Kishanganj district occupies an area of 1,884 square kilometres (727 sq mi),comparatively equivalent to Maui in the United States.Kishanganj district is surrounded by Araria district in the west, Purnia district in the south-west, Uttar Dinajpur district of West Bengal on the east, and Darjeeling district of West Bengal and Nepal on the north. A narrow strip of West Bengal, about 20 km wide separates it from Bangladesh.

In 2006 the Ministry of Panchayati Raj named Kishanganj District as an economically distressed district, one of 250 out of a total of 640 districts.It is one of the 36 districts in Bihar currently receiving funds from the Backward Regions Grant Fund Programme (BRGF).