Most Aragonese rivers are tributaries of the Ebro River, which is the largest river in Spain and divides the community in two. Of the tributaries of the left bank of the river, the ones originating in the Pyrenees, the Aragón River stands out. Its headwaters are in Huesca, but it ends at the community of Navarre, the Gállego and the Cinca, which joins the Segre just before emptying into the Ebro at the height of Mequinenza. On the right bank, the Jalón, Huerva and Guadalope stand out.

In the stream bed of the Ebro river, near the border with Catalonia, the Mequinenza Reservoir, of 1,530 hm3 and a length of about 110 km; it is popularly known as the “Sea of Aragon”.

The small Pyrenean mountain lakes called ibones merit special mention. These lakes are very scenic, originating during the last glaciation, and are usually found above 2,000 m.

The Autonomous Community lies within three hydrographic regions, the Ebro River, the Tagus River (which originates in the Sierra de Albarracín range), and the Júcar, which has as its main river in this community the Turia.