Udayapur District (Nepali: उदयपुर जिल्लाListen , is one of 14 districts of Province No. 1 of 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
Gaighat is an administrative centre within Triyuga Municipality and the headquarter of Udayapur District located in Province No. 1 of Nepal. Gaighat is divided into 2 wards called Gaighat Bazar and Old Gaighat. The Gaighat is located in Ward No. 11 and Old Gaighat is in Ward No. 12 of Triyuga Municipality. Total area of two wards is 16.11 square kilometres (6.22 sq mi) and total population is 14,243 with 2832 households.
Triyuga is one of eight municipalities of Udayapur district of the Province No. 1 of Nepal. Gaighat is the headquarter of the municipality. According to the 1991 Nepal census, it had a population of 55,291. According to the 2011 Nepal census, Triyuga had 87,557 inhabitants. According to the 2021 Nepal census the initial population of the municipality is 104,375. It is divided into 16 wards. Triyuga Municipality was established on B.S. Chaitra 13, 2053. It was named after Triyuga River. A river which flows through the town. Triyuga is the 3rd largest municipality in Nepal and 1st largest in Province No. 1 in term of size (area). The total area of the municipality is 547.43 square kilometres (211.36 sq mi)
Aaptar was a village development committee in Udayapur District in the Sagarmatha Zone of Eastern Development Region of Nepal. It became part of Rautamai Rural Municipality after reconstruction of administration in Nepal.
Basabote was a village development committee in Udayapur District in the Sagarmatha Zone of Eastern Development Region of Nepal. It became part of Limchungbung Rural Municipality after reconstruction of administration in Nepal.
Bhuttar was a village development committee in Udayapur District in the Sagarmatha Zone of Eastern Development Region of Nepal. It became part of Rautamai Rural Municipality after reconstruction of administration in Nepal. It is now municipal headquarter of Rautamai rural municipality.
Iname is a village development committee in Udayapur District in the Sagarmatha Zone of south-eastern Nepal. At the time of the 1991 Nepal census it had a population of 3256 people living in 587 individual households.
Jalpachilaune is a populated place located in Triyuga municipality of Udayapur District in Province No. 1 of Nepal. At the time of 2011 Nepal census it had a population of 3,864 people living in 807 individual households.
Jante is a village development committee in Udayapur District in the Sagarmatha Zone of south-eastern Nepal. At the time of the 1991 Nepal census it had a population of 2142 people living in 385 individual households.
Jogidaha is a populated place located in Triyuga municipality of Udayapur District in Province No. 1 of Nepal. At the time of 2011 Nepal census it had a population of 6,665 people living in 1,451 individual households.
Katari is a Municipality in Udayapur District in the Province No. 1 of south-eastern Nepal.It lies by the Tawa river having the bridge of length 123.5m. This was established by merging two existing village development committees i.e. Triveni and Katari on 18 May 2014. At the time of the 1991 Nepal census it had a population of 7230 people living in 1410 individual households. Thirty years later, Katari had undergone rapid growth, achieving a population of 56,146 people by the 2011 census.
Khanbu is a populated place located in Triyuga municipality of Udayapur District in Province No. 1 of Nepal. At the time of 2011 Nepal census it had a population of 4,350 people living in 782 individual households.
Laphagaun was a village development committee in Udayapur District in the Sagarmatha Zone of Eastern Development Region of Nepal. It became part of Rautamai Rural Municipality after reconstruction of administration in Nepal.
Nametar was a village development committee in Udayapur District in the Sagarmatha Zone of Eastern Development Region of Nepal. It became part of Rautamai Rural Municipality after reconstruction of administration in Nepal.
Okhale is a village development committee in Sindhuli District in the Sagarmatha Zone of south-eastern Nepal. At the time of the 1991 Nepal census it had a population of 2722 people living in 507 individual households.
Panchawati is a village in, and headquarter of, Udayapurgadhi rural municipality in Udayapur District in Province No. 1 of south-eastern Nepal. At the time of the 1991 Nepal census it had a population of 6,580 people living in 1223 individual households.
Pokhari was a village development committee in Udayapur District in the Sagarmatha Zone of Eastern Development Region of Nepal. It became part of Rautamai Rural Municipality after reconstruction of administration in Nepal.
Rauta was a village development committee in Udayapur District in the Sagarmatha Zone of Eastern Development Region of Nepal. It became part of Rautamai Rural Municipality after reconstruction of administration in Nepal.
Triveni is a town in Katari Municipality, Udayapur District, in the Sagarmatha Zone of south-eastern Nepal. The formerly Triveni village development committee was merged to form a new municipality from 18 May 2014. At the time of the 1991 Nepal census, Triveni had a population of 6015 people, living in 1105 individual households.
Chaudandigadhi is a municipality in Udayapur District of Province No. 1 in Nepal that was established on 10 March 2017 by merging the former Village development committees Chaudandi, Siddipur, Hadiya and Sundarpur with the former municipality Beltar Basaha. At the time of the 2011 Nepal census, the localities out of which Chaudandigadhi would be formed had a joint population of 48,574 people living in 10,519 individual households. It is surrounded by Belka Municipality in the east, Triyuga in the west, the districts of Khotang and Bhojpur in the north and Sunsari District in the south.
Nepal 
