OLONETZ, a government of north-western Russia, extending from Lake Ladoga almost to the White Sea, is bounded on the W. by Finland, on the N. and E. by Archangel and Vologda, and on the S. by Novgorod. The area is 57,440 square miles. Its north-western portion belongs orographically and geologically to the Finland region; it is covered with hills reaching 1000 feet in height, and with numberless smaller ridges and hollows running from north-west to south-east. The rest of the government is a flat plateau sloping towards the marshy lowlands of the south. The geological structure is very varied. Granites, syenites, and diorites, covered with Laurentian metamorphic slates, occur extensively in the north-west. Near Lake Onega they are covered with Devonian sandstones and limestones, yielding marble and sandstone for building; to the south of that lake the Carboniferous limestones and clays make their appearance. The whole is covered by vast beds of boulder-clay, the bottom moraine of the great ice-sheet of the Glacial period. The entire region bears traces of glaciation, either in the shape of scratching and elongated grooves on the rocks, or of eskers (åsar, selgas) running parallel to the glacial striation. Numberless lakes, more than 2000 being already laid down on the maps, still occupy the depressions of the surface, while a great many more have left evidence of their past existence in the shape of extensive marshes. Lake Onega covers 3765 square miles and reaches a depth of 125 fathoms. Lakes Seg, Vyg, Lache, and Vodlo cover from 140 to 480 square miles each, and their crustacean fauna shows a former connexion with the Arctic Ocean. The south-eastern part of Lake Ladoga belongs also to the government of Olonetz. Altogether, the area covered by lakes, marshes, and rivers reaches one-fifth of the whole surface. The rivers belong to the Baltic and White Sea basins. To the former system belong Lakes Ladoga and Onega, which are connected by the Svir and receive numerous streams; of these the Vytegra, which communicates with the Mariinsk canal-system, and the Oyat, an affluent of Lake Ladoga, are important for navigation. No less than 4,000,000 cwts. of timber, fire-wood, stone, metal, and flour are annually shipped on waters belonging to this government. The Onega river, which has its source in the south-eastern parts of the government and flows into the White Sea, is of minor importance. Seventy per cent, of the area of Olonetz is occupied by forests; those of the crown, maintained for shipbuilding purposes, cover more than 800,000 acres.

The climate is harsh and moist, the average yearly temperature at Petrozavodsk (61° 8′ N. lat.) being 33°·6 Fahr. (12°·0 in January, 57°·4 in July); the thermometer rarely falls under −30° Fahr. The population, which numbered 321,250 in 1881 (296,400 in 1873), is made up of Great Russians and Finns; Karelians and Tchudis are estimated at about 52,000 each. The people mostly belong to the Greek Church, or are Nonconformists. Sparse though it is, the population is still too dense in certain places when the smallness of the area available for agriculture (only the summits of the selgas, or elongated ridges separated by marshes) is taken into account. The villages are mostly small, and in several parts of the government are still aggregated into federations of communes. Only 765,000 acres were under crops in 1877. Cattle and horse breeding, which are much interfered with by plague, are insignificant. The chief source of wealth is the timber-trade, next to which come fishing and hunting. Mushrooms and berries are exported to St Petersburg. There are also quarries and iron-mines, and some 1600 men find employment in saw-mills, tanneries, iron-works, distilleries, and flour-mills. More than one-fifth of the entire male population leave their homes every year in search of employment. The government is divided into seven districts, the chief towns of which are the capital Petrozavodsk (12,000 inhabitants), Kargopol, Olonetz, Povyenets, Vytegra, and Pudozh. Olonetz includes the "Olonetz Mining District," a territory belonging to the crown, which covers 432 square miles and extends partly into the Serdobol district of Finland. The iron-works were begun by Peter I. in 1701-14. There is a population of about 60,000, who were, until 1864, serfs to the crown.

Olonetz was colonized by Novgorod in the 11th century, and though it suffered much from Swedish invasion its towns soon became wealthy trading centres. Ivan III. annexed it to the principality of Moscow.