Udayapur District (Nepali: उदयपुर जिल्ला, is one of the 14 districts of Koshi Province in eastern Nepal. The district, with Triyuga as its district headquarters, covers an area of 2,063 km2 and in 2001 had a population of 287,689, in 2011 of 317,532, in 2021 of 342,773

The Tharu or Tharuhat languages are any of the Indo-Aryan languages spoken by the Tharu people of the Terai region in Nepal, and neighboring regions of Uttarakhand, Uttar Pradesh and Bihar in India.