Burg Tannenberg, Medieval castle in Nentershausen, Germany.

Burg Tannenberg is a castle in Nentershausen whose stone walls rise above the Richelsdorfer mountains and feature defensive towers alongside architectural elements from the 14th century. The structure displays typical characteristics of a medieval fortress, with visible stonework remains that illustrate the spatial layout and defensive purpose of the former stronghold.

Burg Tannenberg was built in the 14th century on the site of an older fortification that a Hersfeld charter described as abandoned "since ancient times". The earlier Alt-Tannenburg stood on the "old dome" nearby, where ramparts and ditches are still visible, and its stones were reused for the new castle. The three-storey house on the north side was rebuilt under Ludwig VII of Baumbach and completed in 1545 under Ewald of Baumbach; the residential tower was begun around 1375 and raised to its present four storeys in 1555.

The name Tannenberg comes from the spur of the Herzberg above Nentershausen, and the castle is often called Tannenburg. The former Burgwartshaus, rebuilt around 1690, now houses the Burgwirtshaus inn on its ground floor, with its outdoor seating on the site of the old Kemenate. In the west wall, restoration work uncovered a row of arches thought to be Romanesque.

The castle stands about one kilometre east of Nentershausen on a spur of the Herzberg at 351 m. The entrance to the core castle lies on the west side, where the gatehouse foundations and a loophole at today's cellar level were uncovered in 2006. The courtyard runs like a street between the north and south buildings; the ground is uneven, so sturdy shoes help.

Village residents repurposed stones from the castle walls to build their own homes, creating a lasting architectural connection between the fortress and the surrounding community. This practice shows how the castle became part of everyday life after its decline.