COSSIMBAZAR or KASIMBAZAR, a decayed town on the river Bhagirathi in the Murshidabad district of Bengal, India, now included in the Berhampore municipality. Though the history of the place cannot be traced back earlier than the 17th century, it was of importance long before Murshidabad was made the capital of Bengal. In that century it became the great trading centre of Bengal. In 1658 an English factory was established at Cossimbazar, which soon became the chief commercial agency of the East India company in Bengal. French and Dutch factories were also set up in the second half of the 17th century, and the Armenians had a settlement in a suburb of the town. The proximity of the English factory to Murshidabad, the Moham medan capital, while it was the main source of its wealth and political importance, exposed it to constant danger. Thus, in it was the first to be taken by Siraj-ud-daula, the nawab of Bengal; and the resident, with his assistant (Warren Hastings), were taken as prisoners to Murshidabad.
After the famine of 1770 the cultivated area in its neighbour hood shrank and the greater part of the surrounding country was described as "a wilderness inhabited only by beasts of prey." In 1813 its ruin was completed by a sudden change in the course of the Bhagirathi, which formed a new channel 3m. from the old town. Virulent epidemics broke out which swept away three fourths of the inhabitants, and loss of population was followed by dilapidation of buildings. The first wife of Warren Hastings was buried at Cossimbazar, where her tomb, with its inscription, still remains.