PKP Class Pt31 is a Polish steam locomotive of Polskie Koleje Państwowe, designed for hauling heavy long-distance passenger trains, built in 1932-1940.

[1] Three prototypes were built in 1932 and successfully competed with 4-8-2 Pu29 locomotive - both were similar, but more compact Pt31 better suited Polish turntables.

[1] From 1934, a series production for the PKP followed, and by the outbreak of World War II in 1939, 98 were made, numbered Pt31-1 to 98.

[2] During the war, 54 locomotives were captured by the Germans and impressed into service as DR class 191, with numbers 101 to 154.

[3] Remaining 44 Pt31 locomotives were captured by the Soviets in Poland, 21 of them had been converted to broad gauge by 1941, transliterated as ПТ-31 class.