PETROPAVLOVSK, a town of West Siberia, in the government of Akmolinsk, on the right bank of the Ishim river, and on the great Siberian highway, 170 m. by rail W. of Omsk. The population, 7850 in 1865, was 21,796 in 1900, of whom one-third were Mahommedan Kirghiz. The town carries on an active trade in cattle, furs, tea, wool, skins, cottons, woollen stuffs, corn, metals, metallic wares and spirits. The small fort of Petropavlovsk was founded in 1752, and was the military centre of the Ishim line of fortifications.
Petropavlovsk is also the name of a Russian seaport in Kamchatka, on the eastern shore of the Bay of Avacha, In 53° N. and 158° 44′ E. Its harbour, one of the best on the Pacific, is little used, and the town consists merely of a few huts with some 400 inhabitants. Its naval institutions were transferred to Nikolayevsk after the attack of the Anglo-French fleet in 1854.