Watershed of the Oca at Villalbos (Valle de Oca)
|- left||Cerratón, Anguilas, Homino|
|Source||Montes de Oca|
|- location||Rábanos, Montes de Oca, Burgos, Castile and León, Spain|
|- elevation||1,186 m (3,891 ft)|
|Mouth||Horadada Gorge, Ebro river|
|- location||Oña, La Bureba, Burgos, Castile and León, Spain|
|- elevation||570 m (1,870 ft)|
|Length||70 km (43 mi)|
Oca river is the first Ebro tributary river on the right bank (Red spot marks the source of Oca river)
The Oca river is a short river, about 70 km, of the north of Spain, It is an affluent of the Ebro river that flows through the province of Burgos. It is born in the Sistema Ibérico range and it has 70 km of route, crossing of the south to north the municipalities of Rábanos, Villafranca Montes de Oca, Valle de Oca, Alcocero de Mola, Prádanos de Bureba, Briviesca, Vileña, the shire of Bureba and Oña.
Oca River rises in the comarca of Montes de Oca, near the town of Rábanos. Within walking distance of their current source follows the narrow gorge of La Hoz of 700 m long and 100 m high of sheer rocks, Passage of great strategic value, in the eleventh century, defended by the castle of Alba.
On the right receives the waters of the river Matapán and the streams Valsorda and Penches, while on the left receives the waters of the rivers Cerratón, Anguilas and Homino, and the streams Valdazo and Hoyo.
See also 
- Ebro's Water Planning Office