Żyrardów County (Polish: powiat żyrardowski) is a unit of territorial administration and local government (powiat) in Masovian Voivodeship, east-central Poland.

It came into being on 1 January 1999, as a result of the Polish local government reforms passed in 1998.

Its administrative seat and largest town is Żyrardów, which lies 43 kilometres (27 mi) south-west of Warsaw.

The only other town in the county is Mszczonów, lying 11 km (7 mi) south-east of Żyrardów.

The county covers an area of 532.63 square kilometres (205.6 sq mi).