Thurnau castle was built in 1239 by the Förtsch family on a sandstone rock outcrop which rises up out of the surrounding flood plain. The nearby settlement was named “Turnowe” (the early spelling of Thurnau) after this location, meaning “the tower in the water meadow”. The bower (heated apartments and ladies’ chambers) constituted this earliest part of the castle, and, together with two towers, it formed the historical nucleus of the complex.
After the Förtsch family line died out in 1564, the castle passed to the families of Giech and Künßberg by right of inheritance. These two families lived together in the castle for some years, before regular feuding led to the division of the complex in 1576. Henceforth, the Giechs inhabited the area of the upper castle courtyard, whilst the Künßbergs retained the lower courtyard. The split between the two parties proved decisive for the castle’s further development, triggering differing dynamics in terms of construction throughout the subsequent centuries.
The Künßbergs expanded their section of the castle via the addition of an arcade, a gatehouse and the erection of the building now referred to as the Künßberg wing, which was completed in 1675. In 1600, the Giechs began work on the so-called Hans-Georg Building, as well as raising a coach house in 1714. The last extension was the Carl Maximilian Building, which was finished in 1731. A garden in typical baroque style was likewise laid out between 1698 and 1703, receiving a number of improvements in the late 19th century.
On 7th July 1731, the Giech family purchased the Künßbergs’ half of the castle, thereby becoming its sole owners.
The territories belonging to the Giechs became Prussian in 1796, prior to being integrated into the Kingdom of Bavaria in 1810. The last member of the Giech family, Friedrich Carl Lothar von Giech, died in 1938 without progeny. As a result, Hiller von Gaertringen and his family came into possession of the entire property, before it finally passed to the Giech comital charitable foundation in 1972.