The Rajbanshi, also Rajbongshi and Koch-Rajbongshi, are peoples from Lower Assam, North Bengal, eastern Bihar, Terai region of eastern Nepal, Rangpur division of North Bangladesh and Bhutan who have in the past sought an association with the Koch dynasty. Koch-Rajbanshi people speak Kamatapuri, belong to Indo-Aryan languages, though in the past they might have spoken Tibeto-Burman languages. The community is categorised as OBC in Assam and Bihar, and SC in West Bengal. In Nepal they are considered part of the Plains Janjati. In Bangladesh the community is classified as Plains ethnic group under 'Barman'. They are the largest Scheduled Caste community of West Bengal.

The Terai or Tarai is to a lowland region in parts of northern India and southern Nepal that lies to the south of the outer foothills of the Himalayas, the Sivalik Hills and north of the Indo-Gangetic Plain. This lowland belt is characterised by tall grasslands, scrub savannah, sal forests and clay rich swamps. In North India, the Terai spreads from the Yamuna River eastward across Haryana, Uttarakhand, Uttar Pradesh, Bihar and West Bengal. The Terai is part of the Terai-Duar savanna and grasslands ecoregion. Nepal's Terai stretches over 33,998.8 km2 (13,127.0 sq mi), about 23.1% of Nepal's land area, and lies at an elevation of between 67 and 300 m. The region comprises more than 50 wetlands. North of the Terai rises the Bhabar, a narrow but continuous belt of forest about 8–12 km (5.0–7.5 mi) wide.