The "Cantar de mio Cid" is a Spanish epic poem from the 12th century, considered one of the earliest works of Spanish literature. It tells the story of Rodrigo Díaz de Vivar, known as El Cid, a nobleman and military leader who fought for both the Christian and Muslim kingdoms in medieval Spain. The poem highlights themes of honor, loyalty, and the struggle for justice. The narrative follows El Cid's exile from the court of King Alfonso VI and his quest to regain his honor and lands. Throughout the poem, El Cid demonstrates bravery and leadership, ultimately achieving victory in battles against the Moors and restoring his reputation.