Triyuga is a municipality located in the Udayapur district within the Koshi Pradesh of Nepal. Established on B.S. Chaitra 13, 2053, it serves as one of the eight municipalities in its district and is named after the Triyuga River, which flows through the town. The municipality is headquartered in Gaighat.
In terms of geography, Triyuga is the largest municipality in Koshi Pradesh by area and ranks as the third-largest municipality in Nepal overall. It covers a total area of 547.43 square kilometres (211.36 mi2) and is divided into 16 wards. According to the 2021 Nepal census, the municipality has a total population of 103,475.