The Grodzisk Mazowiecki–Zawiercie railway better known as the Central Rail Line, designated by Polish national railway infrastructure manager PKP Polskie Linie Kolejowe as rail line number 4, is a 224 km (139 mi) long railway line in Poland between Zawiercie outside the Katowice urban area and Grodzisk Mazowiecki in the suburbs of Warsaw.

PKP Intercity is a company of the PKP Group responsible for long-distance passenger transport. It runs about 350 trains daily, connecting mainly large agglomerations and smaller towns in Poland. The company also provides most international trains to and from Poland. Trains offer Wi-Fi connectivity.