Pruszków County is a unit of territorial administration and local government (powiat) in Masovian Voivodeship, east-central Poland. It came into being on January 1, 1999, as a result of the Polish local government reforms passed in 1998. Its administrative seat and largest town is Pruszków, which lies west of Warsaw. The county also contains the towns of Piastów, lying north-east of Pruszków, and Brwinów, south-west of Pruszków.