Le Cid is a five-act French tragicomedy written by Pierre Corneille, first performed in December 1636 at the Théâtre du Marais in Paris and published the same year. It is based on Guillén de Castro's play Las Mocedades del Cid. Castro's play in turn is based on the legend of El Cid.
An enormous popular success, Corneille's Le Cid was the subject of a heated polemic over the norms of dramatic practice known as the Querelle du Cid (Quarrel of The Cid.) Cardinal Richelieu's Académie française acknowledged the play's success, but determined that it was defective, in part because it did not respect the classical unities.
Today, Le Cid is widely regarded as Corneille's finest work, and is considered one of the greatest plays of the seventeenth century.