Region Eastern (Purwanchal)
- Total 1,257 km2 (485.3 sq mi)
- Total 625,633
- Density 497.7/km2 (1,289.1/sq mi)
Sunsari District, a part of Kosi Zone, is one of the seventy-five districts of Nepal, a landlocked country of South Asia. The district, with Inaruwa as its district headquarters, covers an area of 1,257 km² and has a population (as of the 2001 census) of 625,633.
The area was originally part of Morang but became its own districts in 1962 when Nepal was divided into 14 zones and 75 districts.
Major cities in Sunsari district are Dharan (the third largest city in Nepal), Itahari, Tarahara, Duhabi, and Inaruwa.