Its administrative seat and largest town is Opoczno, which lies 72 kilometres (45 mi) south-east of the regional capital Łódź.

The history of Opoczno County dates back to the Middle Ages, when its present territory was divided between the castellanies of Skrzynno and Zarnow.

kilometers, with such towns, as Opoczno, Gowarczow, Bialaczow, Odrzywol, Drzewica and Gielniow.

In 1795 Opoczno County was annexed by the Habsburg Empire, and in 1807, it was part of Radom Department of the Duchy of Warsaw.

During World War II, Opoczno County was disbanded and merged into District (Kreis) of Tomaszow Mazowiecki.