Kosmonosy Castle, Renaissance and Baroque château in Kosmonosy, Czech Republic.

Kosmonosy Castle is a Baroque one-storey four-winged building with thirteen window axes per side, its corners marked by two-storey square towers. The east wing holds the main entrance, a five-axis central rison with a portal, volute pilasters and a balcony with vases. The south side and adjacent parts of the east and west wings have Empire facades added in 1835–1836.

The Kosmonosy estate began as a fortress built by the Krajířové z Krajku family; it was first documented in 1571, when Adam Krajíř had it rebuilt, and in 1583 it was recorded as "newly built". In 1628 Gottfried Heinrich von Pappenheim acquired it and had the old fortress rebuilt in Renaissance style. Count Heřman Jakub Černín then had the château rebuilt in Baroque style between 1697 and 1709 to a design by Giovanni Battista Alliprandi.

The castle serves as a place where visitors can observe how Bohemian noble families lived and shaped their residences. The rooms reflect the tastes and choices of the Czernin family, who reshaped the property according to their preferences.

The château stands in the centre of Kosmonosy, just north of Mladá Boleslav. The protected grounds also take in the farmstead building (No. 2), a dwelling house (No. 225), the park with its terrace wall and pond, and the perimeter wall with its gate and vases. The main entrance is in the east wing, through a portal flanked by volute pilasters carrying a balcony with vases.

The castle's large hall, which rises through two storeys in the east-wing risalit, keeps its original 18th-century ceiling and wall paintings and is the only interior space with this decoration preserved. In the second half of the 20th century the building housed a primary school and a dormitory for a secondary economics school, and the hall served as a concert hall while several rooms were converted into flats.