Idstein is a town of about 25,000 inhabitants in the Rheingau-Taunus-Kreis in the Regierungsbezirk of Darmstadt in Hesse, Germany. Because of its well preserved historical Altstadt it is part of the Deutsche Fachwerkstraße, connecting towns with fine fachwerk buildings and houses. In 2002, the town hosted the 42nd Hessentag state festival.