a town of Russia, in the government of Tver,. on Lake Seliger, 108 m. W.N.W. of the city of Tver; pop. 10,457. The climate is damp and unhealthy. The town has, tanneries, and is a centre for the making of boots and shoes, for agricultural implements, fishing-nets and the building of boats. The advantageous site, the proximity of the Smolenskiy Zhitnyi monastery, a pilgrim resort on an island of the lake and the early development of certain petty trades combined. to bring prosperity to Ostashkov. Its cathedral (1672-1685) contains valuable offerings, as also do two other churches of the same century.