| Cidacos River | |
| Subdivision Type1: | Country |
| Subdivision Name1: | Spain |
| Subdivision Type2: | Region |
| Subdivision Name2: | Castile and León Soria, La Rioja |
| Source1 Location: | Puerto de Oncala |
| Mouth Location: | Ebro |
| Source1 Elevation: | 1425m (4,675feet) |
| Mouth Elevation: | 290m (950feet) |
| Length: | 82.8km (51.4miles) |
| Basin Size: | 696km2 |
| Discharge1 Avg: | 2.7m3/s |
| Map: | CuencaDelEbrov1.svg |
| Map Size: | 280px |
The Cidacos River is a tributary of the Ebro. Its source is Los Campos, in Soria, and it flows for 77 km (48 mi) until its reaches the Ebro at Calahorra (La Rioja).
It flows through or past various towns like Villar del Río, Yanguas, Enciso, Peroblasco, Arnedillo, Santa Eulalia Somera, and Bajera, Herce, Arnedo, Quel, Autol, and Calahorra. The river is used for irrigation purposes and is often dried up near Calahorra.