Siemianowice Śląskie (shĕmyänôvē´tsĕ shläN´skyĕ), city (1991 est. pop. 80,600), Śląskie prov., S Poland. A center of the Katowice mining and industrial region, it has ironworks and steelworks and coal mines. Manufactures include machinery and metals. Its first coal mine was opened in 1797. The city has a 19th-century castle.