Frauenfeld Castle, Medieval castle in Frauenfeld, Switzerland.

Frauenfeld Castle stands on a molasse rock above the Murg in the southwest of the old town. Its centre is a 19-metre-high bergfried built around 1230 from large glacial boulders, with oak ceiling beams dated by dendrochronology to about 1231. The adjoining Murgturm, the residential palas, was added at the same time, and in the 14th century the castle was extended with a zwinger and a two-storey structure whose outer walls partly survive.

The fortress began as a fortified tower in the 13th century and was later transformed into an administrative center for the Habsburg territories. This conversion made Frauenfeld an important urban center in the region.

The castle was the seat of the Thurgau Landvögte, who changed every two years in rotation among the seven Old Cantons; from 1712 Bern also took part. The most important household furnishings stayed in the castle so each new Landvogt did not have to bring his own. In the second half of the 14th century the Lords of Hohenlandenberg dug a deep ditch between castle and town after the failed Appenzell attack of 1407.

The castle stands in the southwest of Frauenfeld's old town, above the Murg river. The main tower entrance is on the second floor, reached by a staircase; the ground-floor entrance beside the tower is still in use. The site is a Swiss heritage site of national significance, so check access before visiting.

The castle holds the highest national protection status in Switzerland as a Class A cultural property and is additionally recognized regionally as particularly valuable. This double designation underscores its exceptional importance across both national and regional heritage levels.