La Rioja (Spanish: [la ˈrjoxa]) is an autonomous community and province in Spain, in the north of the Iberian Peninsula. Its capital is Logroño. Other cities and towns in the province include Calahorra, Arnedo, Alfaro, Haro, Santo Domingo de la Calzada, and Nájera. As of 2024, it has a population of 324,184, making it the least populated autonomous community of Spain.

It covers part of the Ebro valley towards its north and the Iberian Range in the south. The community is a single province, so there is no provincial deputation, and it is organized into 174 municipalities. It borders the Basque Country (province of Álava) to the north, Navarre to the northeast, Aragón to the southeast (province of Zaragoza), and Castilla y León to the west and south (provinces of Burgos and Soria).

The area was once occupied by pre-Roman Berones, Pellendones and Vascones. After partial recapture from the Muslims in the early tenth century, the region became part of the Kingdom of Pamplona, later being incorporated into Castile after a century and a half of disputes. From the eighteenth century the Rioja region remained divided between the provinces of Burgos and Soria, until in 1833 the province of Logroño was created, changing the name of the province to La Rioja in 1980 as a prelude to its constitution under a single provincial autonomous community in 1982. The name "Rioja" (from Río Oja) is first attested in 1099.

The region is well known for its wines under the brand Denominación de Origen Calificada Rioja.

The etymology of the toponym Rioja is complex and has been much discussed. The main theories point to different origins: the traditional popular one that makes it correspond to the river Oja, the one that points to the term Rivalia that would be translated as "land of streams", the one that points as germ a nominal tautology in the term rivo Ohia that would mean "river of fluvial bed"; and the very diverse ones that indicate that it would have its origins in the Basque language, for example as union of the words herria and ogia being translated as "land of bread".

Numerous authors from different periods have proposed different theories about it, such as the friar Mateo Anguiano in the 18th century, Ángel Casimiro de Govantes in the 19th century, Menéndez Pidal or Merino Urrutia in the 20th century, or in the 21st century, the researcher Eduardo Aznar Martínez. In addition, there are texts by older authors such as Florián de Ocampo in the 16th century or Rodrigo Méndez Silva in the 17th century, which give an account of the popular etymology of the toponym.

The first written appearances of this toponym as Rioga or Riogam date back to the 11th century, and it can also be found with different spellings such as Rioxa, Riogia, Rivo de Oia, Rivogio or in its definitive form Rioja in texts of later centuries. On the other hand, the oldest document found in which its demonym appears dates from the 13th century, with the spellings riogeñ and riogensi, that is, Riojan (Spanish: riojano).

In the first written appearances of this toponym in the 11th century, the westernmost area of the present-day Spanish region is designated under the same name; therefore, the primitive Rioja was the territory around the basins of the rivers Tirón and Oja, with some divergences in its exact location by different authors. Gradually and as a result of various historical events, the toponym was extended from the Middle Ages, to name a larger region, consisting of seven river valleys, located between the Tirón in the west and the Alhama in the east, which flow into the Ebro, namely La Rioja today.