Possen, Mountain summit in Thuringia, Germany.

Possen is a 431.5 m high mountain of the Hainleite in the Kyffhäuserkreis, about four kilometres south of Sondershausen. On its summit stands the Possenturm, a 42.18 m timber-framed lookout tower built in 1781 on a stone base. South-east of the tower lies a listed ensemble of 18th- and 19th-century buildings with a park, now run as a leisure park.

A hunting lodge named "Zum neuen Jagdhaus auf dem Oberspierschen Forste" was documented in 1670. Prince Günther XLIII of Schwarzburg-Sondershausen had it rebuilt between 1732 and 1738, when it received the name "Zum Possen". The deposed prince Günther Friedrich Carl I lived there from 1835 to 1837, and the estate passed to the state of Thuringia after 1918.

The name Possen probably comes from early modern German "posse" (ornament, later joke), and since 1738 has referred to the former hunting lodge and its surroundings. Today the site hosts events such as dog shows, and the 1967-converted riding hall serves as a leisure hall with billiards and table tennis.

The Possenturm observation tower stands on the summit plateau, reached on foot; its 214 steps lead to the viewing platform. The tower was built in 1781 on a stone base and rises 42.18 m. The surrounding Freizeitpark has a bungalow settlement and a restaurant south of the tower, built between 1976 and 1979.

The 42.18-metre Possenturm on the summit, built in 1781 in just 11 months on a stone base, is considered Europe's oldest and tallest timber-framed lookout tower. In 1823 a Harz travel guide noted it could be seen from the Brocken, "partly with, partly without a telescope".