Mezensky District (Russian: Мезе́нский райо́н) is an administrative district (raion), one of the twenty-one in Arkhangelsk Oblast, Russia. As a municipal division, it is incorporated as Mezensky Municipal District. It is located in the northeast of the oblast and borders with Nenets Autonomous Okrug in the northeast, Ust-Tsilemsky District of the Komi Republic in the east, Leshukonsky and Pinezhsky Districts in the south, and with Primorsky District in the southwest. From the north, the district borders the White Sea. The area of the district is 34,400 square kilometers (13,300 sq mi). Its administrative center is the town of Mezen. Population: 10,330 (2010 census); 13,124 (2002 census); 17,796 (1989 Soviet census). The population of Mezen accounts for 34.6% of the total district's population.

The area was originally populated by speakers of Uralic languages and then colonized by the Novgorod Republic. After the fall of Novgorod, the area became a part of the Grand Duchy of Moscow. Komi started moving to the Mezen in the 14th and 15th centuries. First Russian settlements on the Mezen were mentioned in the 16th century. The lower course of the Mezen, the current area of the district, was where Russian culture existed in its original state, not mixing with the Komi culture. The town of Mezen was founded in the 16th century as Okladnikova Sloboda. The area was at the time located on one of the main ways from central Russia to the Pechora River basin and to the Ural Mountains.

In the course of the administrative reform carried out in 1708 by Peter the Great, the area was included into Archangelgorod Governorate. In 1780, the governorate was abolished and transformed into Vologda Viceroyalty, and Mezen got the town rights. In 1796, the area was transferred to Arkhangelsk Governorate. The current territory of the district was included into Mezensky Uyezd. On December 28, 1917, a new Ust-Vashsky Uyezd with the administrative center in Ust-Vashka (currently Leshukonskoye) was established; however, in 1925 it was merged back into Mezensky Uyezd. In 1929, several governorates were merged into Northern Krai. On July 15, 1929, the uyezds were abolished and Mezensky District was established. It became a part of Arkhangelsk Okrug of Northern Krai.

In the following years, the first-level administrative division of Russia kept changing. In 1930, the okrug was abolished, and the district was subordinated to the central administration of Northern Krai. In 1936, the krai itself was transformed into Northern Oblast. In 1937, Northern Oblast was split into Arkhangelsk Oblast and Vologda Oblast. Mezensky District remained in Arkhangelsk Oblast ever since.

The district is elongated from west to east. A major part of the district belongs to the basins of the Mezen River (with the main tributaries the Pyoza and the Kimzha) and the Kuloy River (with the Nemnyuga and the Soyana), which both end up in the Mezen Bay of the White Sea. Areas on the White Sea coast drain directly into the sea, and some areas in the northeast of the district drain into the Pyosha River and other rivers of the Barents Sea basin.

Almost the whole of the district is covered by coniferous forests (taiga). The northern part of the district is transitional area between taiga and tundra (lesotundra). There are many glacial lakes across the district. The biggest lakes are east of the Mezen, Lake Varsh (shared with Nenets Autonomous Okrug), Lake Pocha, and Lake Vyzhletskoye.

The district also includes Morzhovets Island which separates the Mezen Bay from the entrance of the White Sea. The island is the only part of the district which lies above the Arctic Circle.

The part of the district located east of the Mezen is essentially unpopulated, with the exceptions of the right bank of the river and of several villages in the valley of the Pyoza.