In 1918 Polish State Railways (Polish name: Polskie Koleje Państwowe or PKP) was formed following the First World War after Poland gained independence and took over 2,627 miles of railway lines in the territory formerly under Prussian rule, 2,707 miles from the former Austrian territory and 4,575 miles from the Russians. In 1922 the entire railway network in Poland was divided into 9 districts: Warsaw, Radom, Vilnius, Kraków, Lviv, Stanyslaviv, Katowice, Poznań and Gdańsk. During the interwar period from 1931 to 1939 the construction of the Warsaw Main Railway Station was completed. PKP electrified more than 6,214 miles (10,000 km) of lines from 1936 to 1987.

In 1939 PKP was divided into eight regions; Warsaw, Torun, Poznan, Katowice, Cracow, Radom, Lwow and Wilno, with the headquarters of PKP located in Warsaw. During the Second World War the railway was subjected to widespread bombing WW2 as it was a crucial part of the German war effort and in 1945 PKP began rebuilding the railway under Soviet occupation. Repairs were performed by the main workshops in Brest, Bydgoszcz, Lviv, Łapy, Nowy Sącz, Ostrów Wielkopolski, Piotrowice Śląskie, Poznań, Radom, Pruszków, Stanyslaviv, Stryi, Tarnów, Tczew, Warsaw-Praga and Eastern Warsaw. The 139 mile route built in 1971 to 1977 between Silesia – Zawiercie – Włoszczowa – Idzikowice – Grodzisk Mazowiecki – Warsaw, known as the Central Mainline (CMK), was the largest investment of Polish State Railways after the war.

After 1990, infrastructural investments were abandoned, with the exception of replacement work. The Polish railway network shortened from 14,292 miles to 11,806 miles of which 7,418 miles were electrified. From 1991 the number of passengers using PKP decreased with the closure of some secondary lines and narrow gauge sections. The Polish State Railways Joint Stock Company (Polish name: Polskie Koleje Państwowe Spółka Akcyjna (PKP S.A.) was established on 1 January 2001 as a result of this commercialisation of the Polish State Railways state enterprise.