The Guadalquivir (Spanish pronunciation: [ɡwaðalkiˈβir]) is the second longest river in Spain (after the Tagus), and the longest in Andalusia. The Guadalquivir is 657 kilometers long and drains an area of about 58,000 square kilometers. It begins at Cañada de las Fuentes in the Cazorla mountain range (Jaén), passes through Córdoba and Seville and ends at the fishing village of Bonanza, in Sanlúcar de Barrameda, flowing into the Gulf of Cádiz, in the Atlantic Ocean. The marshy lowlands at the river's end are known as "Las Marismas". It borders Doñana National Park reserve.
The Guadalquivir river is the only great navigable river in Spain. Currently it is navigable to Seville, but in Roman times it was navigable to Córdoba.
The ancient city of Tartessos was said to be have been located at the mouth of the Guadalquivir, although its site has not yet been found. Tartessos in Basque language means between seas (Atlantic and Mediterranean).
The name comes from the Arabic al-wādi al-kabīr (الوادي الكبير), 'The Great Valley'. Classical Arabic Wadi is pronounced in present-day Maghreb as Oued. The Phoenicians named the river Baits, later Betis (or Baetis) from Pre-Roman times to the Al-Andalus period, giving its name to the Hispania Baetica Roman province. An older Celtiberian name was Oba (gold river), leading to the assumption that etymologically Córdoba means city on the Oba (Cart-Oba).