Hartenstein is a town in the Zwickau district, in Saxony, Germany. It is situated on the river Zwickauer Mulde, 14 km southeast of Zwickau. …Hartenstein is a town in the Zwickau district, in Saxony, Germany. It is situated on the river Zwickauer Mulde, 14 km southeast of Zwickau. The county of Hartenstein was owned by the House of Schönburg from 1406 until 1945.