Battle of Bzura (also known as Battle of Kutno) took place during the Second World War, Polish September Campaign between 9 September, 1939 and 18 September, 1939 and was fought between Polish and German Nazi forces.

It was the largest battle during this campaign. It took place near the Bzura river west of Warsaw. It was the Polish attempt at a counterattack, which failed after an initial success.

Polish forces consisted of Armies 'Poznań' and 'Pomorze'. German forces consisted of Armies 8 and 10 from Army Group Sud .

The battle can be divided into 3 phases:

• Phase I - Polish offensive on Stryków (9-12 September)
• Phase II - Polish offensive on Łowicz (13-16 September)
• Phase III - Polish retreat towards Warsaw and defeat