Appenzell Castle, 16th-century stone mansion in Appenzell, Switzerland

Appenzell Castle is a stone patrician house built between 1561 and 1563, with a square plan over four storeys, a round stair tower and a portico. Its Gothic structure incorporates Renaissance elements, and it is one of the few 16th-century stone buildings in Appenzell.

Appenzell Castle was built between 1561 and 1563 as a patrician mansion for the wealthy doctor Antoni Löw, a leader of the Protestant Reformation in Appenzell. In 1584 the Catholic authorities condemned Löw to death and the building passed to the town, which gave it to the Franciscan nuns until they moved to the neighbouring convent in 1682. It then passed to Antoni Speck, and in 1875 Doctor Anton Alfred Sutter installed his practice there, giving it the name "Doktorhaus".

The castle displays features of the Appenzell regional building style that remain visible in its architecture today. This design shapes the town center's appearance and stays evident to visitors walking through the old town.

The building is centrally located and easily reached on foot by visitors. Access is available at Poststrasse 5 with regular bus connections to Appenzell train station.

The building is not a fortress but a patrician stone house of 1561–1563, with a square plan over four storeys, a round stair tower and a portico. Its crossed double-ridge roof and Gothic structure with Renaissance elements are what a visitor should look at.