The bombing of Wieluń is considered by many to be the first major act of World War II, and the September Campaign. After Luftwaffe air units moved into Polish airspace in the early morning of 1 September, they reached the town of Wieluń by 04:40–45. Around this time, the first strikes on the town were conducted, with a total of 46,000 kg bombs being dropped on civilian targets for 9 consecutive hours. Elsewhere, the Battle of Westerplatte and Danzig skirmishes began around the same time (04:45), starting the well-coordinated Invasion of Poland.

Wieluń is a town in south-central Poland with 21,624 inhabitants (2021). The town is the seat of the Gmina Wieluń and Wieluń County, and is located within the Łódź Voivodeship. Wieluń is a capital of the historical Wieluń Land.