Kosi is one of the fourteen zones of Nepal. The headquarters of Kosi Zone is Biratnagar. It is also its largest city. Other cities of Kosi Zone are Inaruwa, Dharan, Dhankuta and Itahari. Its main rivers are the Arun, Tamar and Sapta Koshi. Kosi has six districts. These are Bhojpur, Dhankuta, Morang, Sankhuwasabha, Sunsari and Terhathum.