Marktkirche (English: Market Church) is the main Protestant church in Wiesbaden, the state capital of Hesse, Germany. The neo-Gothic church on the central Schloßplatz (English: Palace Square) was designed by Carl Boos and built between 1853 and 1862. At the time it was the largest brick building of the Duchy of Nassau. It is also called Nassauer Landesdom (Cathedral of Nassau).
On 27 June 1850, Wiesbaden's main church, the medieval church of St. Mauritius, was destroyed in a fire. After a report showed that its remaining outer walls were not sufficiently stable, it was decided to build a new church. On 26 January 1851, Carl Boos was appointed the architect. Boos submitted proposals for three different locations, namely the old church site at the Mauritiusplatz, the central Schlossplatz facing the Stadtschloss Wiesbaden, and a site in the vineyards on the slopes of the Taunus.
Since the new building should reflect the need for representation of the Nassau residence and emerging spa destination, the site of the former church in the old city was rejected. The five ministers and the parish council preferred the location in the vineyards on the hill, so that the new church would be visible from a distance, but were overruled by six lay people who preferred a central location on the Schlossplatz. The Duke of Nassau made the property available for the construction, but did not sponsor the construction costs.
Carl Boos received the contract without a competition. On 14 January 1852, he presented first plans, but changed them on 25 February 1852, proposing a brick building based on the model of Karl Friedrich Schinkel's Friedrichswerder Church in Berlin. His unusual design with five towers was criticised because of needing too much material and building too high, but he even increased the height of the main tower to about 98 m (300 feet). The foundation stone was laid on 22 September 1853. When the church was completed it was the largest brick building of the Duchy of Nassau.