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.