thumb|right|250px|[[Chuquiraga jussieui growing near a lake in the park.]]
thumb|250px|A lake in El Cajas.
thumb|Park entrance.
thumb|Low clouds.
thumb|Scenic view within the park
El Cajas National Park or Cajas National Park () is a national park in the highlands of Ecuador. It is located about 30 km west from Cuenca, the capital of the province of Azuay. The area of 285.44 km<sup>2</sup> (28,544 ha) between 3100m and 4450m above sea level is characterized by páramo vegetation on a jagged landscape of hills and valleys. It was declared a National Park on November 5, 1996 by resolution N° 057. It is one of 759 UNESCO-designated biosphere reserves in 136 countries.
Name
The name "Cajas" is derived from the Quichua word "cassa" meaning "gateway to the snowy mountains". or "caxa" (Quichua:cold). It has also been linked to the Spanish word "cajas" (boxes).
Ecology
Flora
Humidity and high altitude with low atmospheric pressure create an ecosystem that accumulates organic material in the soil that is able to retain water. The high grassland ecosystem (páramo) contains plants suitably adapted to it, 19 of them endemic to Cajas. The dominant plant is straw grass (Calamagrostis intermedia).
Above 3,300 meters the "queñua" or "paper tree" (Polylepis) forest is found. It is in forests such as these that a second protected population of the rare Fuchsia campii, in the family Onagraceae, is predicted to live, as it has also been found in another nearby national park of similar ecological characteristics.
In the lower parts of the park, the cloud forest and perennial high mountain forest are present, primarily in the ravines near the brooks and rivers.
Fauna
The Cajas National Park is home to a large variety of animals, some of which are endemic or highly endangered. Among the most prominent are the South American condor, of which only 80 remain throughout all Ecuador; the curiquinga, a large black and white raptor, and the largest hummingbird of the world, the giant hummingbird (Patagona gigas), which lives only on agave flowers. The violet-throated metaltail (Metalura gorjivioleta) is endemic to Cajas and surrounding valleys. The avifauna consists of 157 bird species, making birdwatching an alluring activity for visitors.
Overall, forty-four mammalian species have been identified in the park. Species include types of opossums, cats, and bats. Also there are pumas, coatis, weasels, skunks, foxes, porcupines, pacas, shrews, rabbits and other rodents. Endemic are the Cajas water mouse (Chibchanomys orcesi) that belongs to the group Ichthyomyini and Tate's shrew opossum (Caenolestes tatei).
Archeology
The area shows evidence of human activities already from the Cañari period. This includes three interregional roads connecting Guapondelig (later Tomebamba, today Cuenca) with the lowlands including Paredones, a control point for the trade between the highlands and the coastal areas. After the Incan invasion Inca roads were constructed, incorporating preexisting roads. Twenty-eight archeological sites have been identified in the park and its vicinity that indicate inhabitation during the pre-Incan and Incan periods.