The Lagunas de Ruidera Natural Park is a protected natural area and one of the great wetlands of importance located in the Spanish autonomous community of Castilla-La Mancha. The natural park is formed by a group of sixteen backwaters or fluvial lagoons along the valley of the Guadiana Viejo, as a continuation of the river Pinilla by its south-eastern inflow, and by its north-eastern inflow along the Arroyo Alarconcillo; separated and connected to each other by barriers of tuffaceous or travertine formation. The difference in height between them means that the water flows through streams, waterfalls and cascades from one lagoon to the other. Although man-made, the Peñarroya reservoir is also part of the park, due to its contribution to the management of water resources. From a hydrological-structural point of view, these fluvial lagoons are classified as hydro-wetlands.

The natural park is divided between the municipalities of Argamasilla de Alba, Ruidera, Alhambra (without lagoons), Ossa de Montiel and Villahermosa. Within the boundaries of the park are also the castle of Peñarroya, the ruins of the castle of Rochafrida, the cave of Montesinos where Cervantes made Don Quixote spend a night and the King's house in the village of Ruidera.

Rather than true lagoons, these are backwaters caused (according to the most widespread model, among others) by large collapses of the riverbed due to karstic phenomena of a succession of connected dolines separated and related to each other by barriers of tuffaceous formation, which form waterfalls and streams that link each of these lagoons with the next one below, overcoming a drop of more than 140 metres for about 18 km (Blanca lagoon: elevation 870 m; Peñarroya reservoir: elevation 730 m).

The Peñarroya reservoir is also included as a separate artificial formation within the same natural park. Of these "backwaters", only Laguna Taza (artificially drained) and Laguna Blanca could be considered as true lagoons, i.e. separated from the flow of the river along the banks. The Laguna Blanca, where the Pinilla river flows into it, sometimes behaves as a "spring lagoon", yielding, in extraordinary times, spring water.

The Ruidera lagoons have been the setting for the filming of the film Miguel and William, a Spanish-English production about the life of Cervantes and Shakespeare, as well as for the film El Capitán Trueno (Captain Thunder).