Burg Waldeser, Medieval castle ruins in Dessau-Roßlau, Germany.

Burg Waldeser are castle ruins near Dessau-Roßlau, located just outside the city where the Pelze and Mulde rivers meet. The site sits within a protected nature reserve and is accessible by way of marked trails that wind through the surrounding landscape.

The castle was founded in 1212 and served as a residence for the von Waldeser family. Heavy flooding between 1314 and 1325 caused serious damage, and its stones were later taken to build another castle in the city.

The castle bore the name of the von Waldeser family who lived there and held power in the region. Today its remnants stand as reminders of a dynasty whose authority eventually shifted to other structures and places.

The castle site lies about 2 km northeast of Dessau-Roßlau, in the angle where the Pelze flows into the Mulde, inside the Middle Elbe Biosphere Reserve. Nothing of the castle stands today, so there are no walls, foundations or visitor facilities to see; the spot is reached by paths through the floodplain. The village name lives on in the nearby district of Waldersee, renamed in 1935.

The castle was demolished after the Mulde flood of 1314–1325, and in 1341 its stones were used to build Dessau Castle. The place name was only reinterpreted as Waldersee in the 15th century, after castle and village had been destroyed.