Peña del Oso, Mountain summit in Sierra de Guadarrama, Spain.

Peña del Oso, also called Pico del Oso, is a 2,196-metre summit in the Sierra de Guadarrama, in the municipality of El Espinar, southern Segovia province. It is the second-highest peak of the La Mujer Muerta ridge, one metre below La Pinareja. Its north face drops toward the Segovia plain, while the south slope belongs to the Río Moros valley; the summit and much of the north face are covered by one of the range's largest boulder fields.

The summit formed from granite geology that has been exploited since past centuries. A quarry on the southern face supplied local communities with stone for buildings and construction throughout history.

The summit is part of the La Mujer Muerta chain, where the silhouette resembles crossed hands when viewed from the Segovia plain. This visual identity has shaped how locals and visitors perceive the surrounding landscape.

The easiest access starts from Navas de Riofrío, where trails climb through forest and open terrain toward the peak. Weather can shift quickly at this elevation, so sturdy footwear and appropriate clothing help ensure a safe and comfortable hike.

The small granite animal at the geodesic vertex on the summit is what gives the mountain its name; it appears to be a bear. Seen from the Segovia plain, this summit forms the crossed hands on the belly of the La Mujer Muerta silhouette.