St. Martin is the name of a Catholic parish and church in Idstein, Rheingau-Taunus-Kreis, Germany. The official name of the church is Katholische Pfarrkirche St. Martin. The name of the parish became St. Martin Idsteiner Land on 1 January 2017, when it was merged with five other parishes. The parish is part of the Diocese of Limburg.

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.