El Cantar de mio Cid, or El Poema de mio Cid ("The Song of My Cid"; "The Poem of My Cid"), is an anonymous cantar de gesta and the oldest preserved Castilian epic poem. Based on a true story, it tells of the deeds of the Castilian hero and knight in medieval Spain Rodrigo Díaz de Vivar—known as El Cid—and takes place during the eleventh century, an era of conflicts in the Iberian Peninsula between the Kingdom of Castile and various Taifa principalities of Al-Andalus. It is considered a national epic of Spain.
The work survives in a medieval manuscript which is now in the Spanish National Library.
