The 25th Infantry Division (Polish: 25 Dywizja Piechoty) was a unit of the Polish Army in the interbellum period, created in 1921 with headquarters in Kalisz. It consisted of the following regiments:
During the Polish September Campaign the Division, under General Franciszek Alter, was part of the Poznań Army. It took part in the border battle, defending Krotoszyn on September 1, 1939. However, parts of the 56th Infantry Regiment were defeated near Rawicz.
For the next days, the Division was in retreat, together with the whole Army. On September 8, it was positioned near Koło, then it took part in the Battle of the Bzura, attacking the Germans at Ozorków and Łęczyca. In the evening of September 9, the Division managed to recapture Łęczyca, but a few days later it was ordered to retreat. On September 17, the unit managed to force its way into the Kampinos Wilderness, where it soon afterwards engaged in bloody skirmishes. After September 20, remnants of the Division reached Warsaw, taking part in the defence of the city.