Kościan County (Polish: powiat kościański) is a unit of territorial administration and local government (powiat) in Greater Poland Voivodeship, west-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 Kościan, which lies 40 kilometres (25 mi) south-west of the regional capital Poznań.

The county covers an area of 722.53 square kilometres (279.0 sq mi).

The county is subdivided into five gminas (one urban, three urban-rural and one rural).