Siemianowice Śląskie, city, Śląskie województwo (province), south-central Poland. It is a northern suburb of Katowice and is situated in the Upper Silesia coalfield and industrial district. Incorporated in 1932, it developed as a centre of coal mining, ironworking, and steelworking. Though heavy industry fell into decline by the end of the 20th century, the economy still relies on manufacturing (machine parts, chemicals, and construction materials). Pop. (2011) 70,170.