The Yesa Reservoir is located in the Pyrenees, and is formed with the damming of the Aragon River, in the Navarre town of Yesa (Spain), although the largest area of the reservoir is located in the province of Zaragoza, extending from east to west. It is located to the northwest of the Aragonese province of Zaragoza and to the east of Navarre. Most of it floods lands of the Berdun Canal, in the Aragonese region of Jacetania in the municipalities of Sigüés, Ruesta, Escó, and Tiermas. It is known by the nickname Mar de los Pirineos (English: sea of the Pyrenees) and is located at the entrance of the aforementioned. It is the largest navigable area of Aragon and it is the source of the Bardenas Canal that transfers water to the Ribera area south of Navarra and irrigates the Bardenas Reales and the Cinco Villas region of Zaragoza. It is also used for water supply and as a power station.
It has a capacity of 446.86 hm³. The length of the tail end of the reservoir is 10 km with widths varying between 1 and 2.5 km. It occupies an area of 1900 hectares.
The richness of fish in the waters of the Aragón river, with abundance of trout, carp, and American perch makes the banks of the reservoir a very popular place for fishing enthusiasts.
