Pusur River, distributary of the Padma River (Ganges [Ganga] River), southwestern Bangladesh. It leaves the Madhumati River (there called the Baleswar) northeast of Khulna city and flows some 110 miles (177 km) southward past the port at Mongla and through the swampy Sundarbans region to the Bay of Bengal. In its upper course it is called the Atharabanki.