The Kamala Valley, also called Udayapur Valley () is in Udayapur district in southeastern Nepal (Sketch map). It is about long and between and wide. It is drained by the Triyuga river flowing east to join the great Koshi. This valley lies between the Mahabharat Range to the north and the Sivalik Hills to the south, with an average elevation of about . Triyuga is the main town.