Mszczonów [ˈmʂt͡ʂɔnuf] is a town in Żyrardów County, Masovian Voivodeship, Poland, with 6,231 inhabitants as of the 2006 census.

The oldest known mention of Mszczonów comes from a document of Duke Konrad I of Masovia from 1245, when it was part of fragmented Piast-ruled Poland.

One of two main routes connecting Warsaw and Dresden ran through the town in the 18th century and Kings Augustus II the Strong and Augustus III of Poland often traveled that route.

[2] During the invasion of Poland, which started World War II in September 1939, the town was invaded by Nazi Germany.

On September 8, 1939, German troops murdered 11 Polish prisoners of war in the town,[3] and on September 11, 1939, the Germans carried out a mass execution of 20 local Poles, including mayor Aleksander Tański, two priests and a doctor (see Nazi crimes against the Polish nation).