Les Gorges de la Fou (tautology) or better La Fou is a gorge in the stream called la Fou, a tributary of the Tec, between the northern Catalan municipalities of Cortsaví and Montferrer, but very close to that of Arles from where the visitable route leaves, all three located in the region of Vallespir, in Northern Catalonia .

The depth, length and narrowness of the passage opened by the water in the limestone rock are: 1.7 kilometers long, 150 m deep, and a separation that, at the bottom, is often no more than a meter. In order to enhance its tourist attractions, a metal footbridge has been installed that allows a ninety-minute route along one and a half kilometres, with slopes of 9% and a width of one metre. The gorge has been described as "the narrowest gorges in the world".

There is a network of underground galleries and grottoes arranged both along and at the height of the gorges, which are not open to tourist visits.