It is the smallest of Spain and minor population. Its name comes from the river Oja that crosses it. Its identity origin is related to the disputes between the Kingdoms of Castile, Navarre and Aragon for its territorial expansion in the epoch of the Reconquest. In medieval epoch, the Way of Santiago, stimulated its economy. In the 17th century its lands were distributed between Burgos and Soria until in 1821 they are reunified. After later allotments and reunification, the Community occupies minor extension that the natural and historical space of La Rioja. It is a cradle of the Castilian language, the annotations of Emilian, the first commentaries in Spanish in a book in Latin written in San Millán de la Cogolla's monastery. Gonzalo de Berceo wrote the first complete verses in popular language.

They are presided by La Demanda mountain range, with the Peak of San Lorenzo as highest point of the province (2271 m.). Traditionally it is distinguished among:

- Rioja Alta, western region zone, from La Demanda mountain range up to the Ebro. It is mountainous, humid, colder and rainy than the rest of the Autonomy.

- Rioja Baja, eastern region zone delimited by the Ebro and the river Leza. It occupies the regions watered by the rivers Alhama and Cidacos. Trowel, with bigger influence of the continental Mediterranean climate proper of the Ebro depression.

The capital and its region is among both Riojas.

It is possible to distinguish:

- The Ebro valley, in the northern part

- The spurs of the Iberian System, with special importance La Demanda mountain range, subdivided in the San Lorenzo mountain range in the northern part and that of Castejón in the southern part, between the Viniegras. Both are separated by the river Najerilla.

With bigger rainfalls and minor temperatures than the rest of the Ebro valley. It changes of Rioja Alta, colder and rainy than Rioja Baja, more influenced by the Mediterranean proper climate of the Ebro Valley.

The natural vegetation is very degraded by the man action, who gave priority to the pasture creation opposite to the primitive beeches forest. This way bushes have arisen with broom and juniper.

Its rivers are going to end in the right margin of the river Ebro. There are the rivers Oja, Najerilla, Iregua, Leza and Cidacos, this one with a very fertile valley.