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. It is divided into 16 wards. Triyuga Municipality was established on B.S. Chaitra 13, 2053 (26 March 1997). 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