| Unionskirche | |
|---|---|
 Interior facing the altar, in 2017 after restoration | |
 | |
| 50°13′15″N 8°16′11″E / 50.22083°N 8.26972°E | |
| Location | Idstein |
| Country | Germany |
| Denomination | Protestant Church in Nassau |
| Website | www |
The Unionskirche (Union Church) is the active Protestant parish church of Idstein, a town in the Rheingau-Taunus district in the German state of Hesse. Idstein was a residence of the counts of Nassau. The church building in the center of the historic Altstadt (old town) dates back to the 14th century when it was built as a collegiate church. It became Lutheran during the Reformation. Its interior was adapted in the 17th century to become a Lutheran Predigt- und Hofkirche (sermon and court church). The most prominent decoration in the church is the series of 38 paintings by the Flemish painter Michael Angelo Immenraedt, an exponent of Flemish Baroque painting, and others. They follow a program of biblical scenes.
The church was named Unionskirche in 1917 to commemorate the union of Lutheran and Reformed Protestants in the Duchy of Nassau in August 1817, the first of its kind (before the Prussian Union in September of the same year). The Unionskirche is a recognized monument under the Hague Convention. It is used by the Protestant congregation, and it is open to other institutions as a concert venue, including concerts of the Rheingau Musik Festival. It features an organ built in 1912 by Walcker Orgelbau and retaining the historic case dating back to 1783.
The church was restored from 2012 to 2017, completed for 500 years since the Reformation and 200 years since the Union. The restoration was awarded the Hessischer Denkmalschutzpreis (Hessian monument preservation prize).