The Poppenberg is a tree-covered mountain east of Ilfeld in the Harz mountains of Germany, with a height of 601 metres. Since 1897, there has been a 33 metre high steel lattice observation tower on the summit. The tower was built by the Nordhausen branch of the Harz Club and was named after Otto, Prince of Stolberg-Wernigerode. In good weather, it has an extensive view over the South Harz, the Goldene Aue and the Kyffhäuser.
The Poppenberg is no. 92 in the system of check points in the Harzer Wandernadel network of walking trails.