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.

Francisco Javier Castaños Aragorri, 1st Duke of Bailén (1758–1852) was a Spanish military commander during the French Revolutionary Wars and the Napoleonic Wars. He presided over the Regency Council of Spain and the Indies, in 1810. From July to September 1834, he served as the first president of the Senate of Spain, at that time called the House of Peers.