Nagarain is a municipality in Dhanusha District in Province No. 2 of south-eastern Nepal. As of 2011 Nepal census, it has a population of 36,336 living in 6,478 individual households. It was formed by joining Fulgama, Devdiha, old Nagrain, Lagmagadha Guthi and Ghodghans village development committees. The total area of Nagarain municipality is 38.71 km2.