Unionskirche, Idstein

Unionskirche
Interior facing the altar
50°13′8″N 8°16′0″E / 50.21889°N 8.26667°E / 50.21889; 8.26667Coordinates: 50°13′8″N 8°16′0″E / 50.21889°N 8.26667°E / 50.21889; 8.26667
Location	Idstein
Country	Germany
Denomination	Protestant Church in Nassau
Website	www.ev-kirche-idstein.de

The Unionskirche (Union Church) is the active Protestant parish church of Idstein, a major town in the German Rheingau-Taunus District. 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. 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.

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.

Remnants in the tower prove that a Romanesque church existed before 1287 at the same location. The oldest part of today's church is the 13th century base of the north tower bordering on the choir. The present church was built from 1330 to 1350 under Gerlach, count of Nassau, as the church for a Collegiate of six canons, founded in 1333. Collegiate and church were dedicated to St. Martin.

Idstein became Protestant during the Reformation. After the Thirty Years' War, the church was transformed into a representative Baroque "Predigt- und Hofkirche" (sermon and court church) by Johann of Nassau-Idstein (1603–77). The rebuilding lasted from 1665 to 1677. Whereas the basilica nave was kept, the church was expanded to the west, the walls were raised resulting in flatter roofs. Most of the pillars were removed, oval windows were installed in the clerestory, and portals rounded. The interior was changed from 1665. Arnold Harnisch (Mainz) and Hans Martin Sattler (Idstein) removed the vaults and built "Marmorarkaden" (arcades of marble). Galleries were installed on three sides in 1675.