Sieradz County (Polish: powiat sieradzki) is a unit of territorial administration and local government (powiat) in Łódź Voivodeship, central Poland. It was created on January 1, 1999 as a result of the Local Government Reorganization Act of 1998. Its administrative seat and largest town is Sieradz, which lies 54 kilometres (34 mi) west of the regional capital Łódź. The county contains three other towns: Złoczew, lying 23 km (14 mi) south-west of Sieradz, Warta, lying 14 km (9 mi) north-west of Sieradz, and Błaszki, 23 km (14 mi) west of Sieradz.
The county covers an area of 1,491.04 square kilometres (575.7 sq mi). As of 2006 its total population is 121,013, out of which the population of Sieradz is 44,045, that of Złoczew is 3,403, that of Warta is 3,388, that of Błaszki is 2,179, and the rural population is 67,998.
The county is subdivided into 11 gminas (one urban, three urban-rural and seven rural). These are listed in the following table, in descending order of population.