The Ordesa Valley is a glacial valley in Aragon, in the Spanish Pyrenees which forms part of the Ordesa y Monte Perdido National Park. It was first discovered in 1820, but not mapped in detail until approximately the 1920s. The valley is about 11 kilometres (7 mi) long.
Monte Perdido (3,355 m) is the third highest mountain in the Pyrenees and together with Cilindro de Marboré (3,328 m) and Soum de Ramond (3,263 m) can be seen at the north-east end of the valley. The name Monte Perdido (lost mountain) was given because the peak could not be seen from the French side of the range.