The Ustya (Russian: Устья) is a river in Kotlassky, Krasnoborsky, Ustyansky, and Velsky Districts of Arkhangelsk Oblast in Russia. A very short portion of the river also forms the boundary between Kotlassky District and Velikoustyuzhsky District of Vologda Oblast. It is a right tributary of the Vaga River. The length of the river is 477 kilometres (296 mi). The area of its basin 17,500 square kilometres (6,800 sq mi). Its main tributaries are the Kizema River and the Kokshenga River (both left). The name of Ustyansky District originates from the Ustya River.