Scharfenstein Castle, Rock castle in Drebach, Germany.

Scharfenstein Castle is a rock castle perched on a narrow ridge above the Zschopau valley in the Ore Mountains of Saxony, Germany. The complex consists of several stone buildings arranged along the ridge, enclosed by a surrounding wall and anchored by a tall residential tower.

The castle was founded around 1250 by the lords of Waldenburg to control the passage through the Zschopau valley. A fire in 1921 destroyed much of the structure, and the subsequent reconstruction followed the original plans so closely that the building kept its medieval form.

The castle's name, first recorded in 1350, refers to the sharp-edged rock spur above the Zschopau. Since 1995 its rooms have housed exhibitions, and the bergfried serves as an observation tower. The nearby Gänsewinkel is the 1762 birthplace of Karl Stülpner, a poacher around whom local legends grew.

The castle is reached on foot along a forest path that starts from the village of Drebach below. Guided tours lead through the interior rooms, and climbing the tower at the end gives a broad view over the valley and the surrounding hills.

In 1932 the owner Fritz Eulitz set up a bird observatory on the estate: hundreds of nest boxes were hung in its 325 hectares of woodland, birds were ringed and reports published with the Chemnitz Ornithological Society. The bergfried still serves as an observation tower today.