Třinec (Czech pronunciation:[ˈtr̝̊ɪnɛts]; Polish: Trzyniec , German:Trzynietz) is a town in Frýdek-Místek District, Moravian-Silesian Region of the Czech Republic. It lies on the Olza River, in the historical region of Cieszyn Silesia. The town has 37,405 inhabitants as of 2009, in 2001 17.7% of the population were Poles. The town is notable for its steel plant, the Třinec Iron and Steel Works, largest one in the Czech Republic, which still has a major impact on the town, on its character, demographics and air pollution.