The Mezen is a river in Udorsky District of the Komi Republic and in Leshukonsky and Mezensky Districts of Arkhangelsk Oblast in Russia. Its mouth is located in the Mezen Bay of the White Sea. Mezen is one of the biggest rivers of European Russia. It is 966 kilometres (600 mi) long, and the area of its basin 78,000 square kilometres (30,000 sq mi). The principal tributaries of the Mezen are the Bolshaya Loptyuga (left), the Pyssa (left), the Mezenskaya Pizhma (right), the Sula (right), the Kyma (right), the Vashka (left), the Pyoza (right), and the Kimzha (left).