Bailén is a town in the province of Jaén, Spain.

The Battle of Bailén was fought in 1808 between the Spanish Army of Andalusia, led by General Francisco Javier Castaños and the Imperial French Army's II corps d'observation de la Gironde under General Pierre Dupont de l'Étang. This battle was the first open-field defeat of a Napoleonic army. The heaviest fighting took place near Bailén, a village by the Guadalquivir river in the Jaén province of southern Spain.