The Cidacos River is a tributary of the Spanish Ebro River. Its source is Los Campos, in Soria, and it flows for 77 kilometres (48 mi) until it 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.

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  The Cidacos near Autol
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  Bridge over the Cidacos near Arnedillo

• List of rivers of Spain

42°12′38″N 2°12′21″W / 42.21056°N 2.20583°W / 42.21056; -2.20583