KOZELSK, a district town of the government of Kaluga in European Russia, situated 43 miles south-west of Kaluga, on the left bank of the river Zhizdra. The principal building is the cathedral, erected in 1700, and rebuilt by Catherine II. after the fire of 1777. In the first half of the present century sailcloth was largely manufactured in the town; but this industry has declined, and, though there are oil-mills, tanneries, rope-walks, and breweries, many of the working classes have to seek employment elsewhere. Population in 1870, 13,400.

Kozelsk emerges in the middle of the 12th century. In 1238 it was utterly destroyed, and all its inhabitants put to the sword by the Tartar invaders. During the 15th century it formed a bone of contention between the Lithuanian princes and the grand-dukes of Moscow. Ivan the Terrible surrounded it with a wooden palisade. Captured by Dolgonιkoff in 1607, it withstood a heavy siege at the hands of Ismailoff.