El Cantar del Mio Cid is the oldest preserved Spanish cantar de gesta. Formerly, it was transmitted only orally, but in 1142 it was written down by a certain Per Abbat. This copy is held as part of a 14th century codex in the Biblioteca Nacional de España (National Library) in Madrid. However, it is incomplete. The first page and two others in the middle are missing. It is written in medieval Spanish, the ancestor of modern Spanish.
Its current title is a modern invention by Ramón Menéndez Pidal; its original title is unknown. Some call it El Poema del Cid on the grounds that it is not a cantar but a poem made up of three cantares. The title has been translated into English as The Lay of the Cid and The Song of the Cid. Some English translations include the verse translation of W.S. Merwin and prose translation of Rita Hamilton and Janet Perry.

The story
El Cid has to leave Castile and fights with the Moorish king of Zaragoza until he gets to Valencia

Cantar del Destierro
El Cid conquers Valencia. After Cid asks the king to forgive him, he agrees and Cid marries his two daughters to the infantes (a nobility title) of Carrión.

Cantar de las Bodas
The infantes of Carrión offend and abandon their wives. Once more, El Cid has to gain his honor back, so he asks the court of Toledo for justice. Then he remarries his two daughters to the infantes (sons of the kings) of Navarre and Aragon. Through the marriages of his daughters, the Cid begins the unification of Spain.

Authorship and composition date
These are the first two stanzas that we have. The format has been slightly regularised.
De los sos oios tan fuertemientre llorando,
Tornava la cabeça e estavalos catando;
Vio puertas abiertas e uços sin cañados,
alcandaras vazias, sin pielles e sin mantos
e sin falcones e sin adtores mudados.
Sospiro Mio Cid, ca mucho avie grandes cuidados.
Fablo mio Cid bien e tan mesurado:
«grado a ti, Señor, Padre que estas en alto!
»Esto me an buelto mios enemigos malos.»
Alli piensan de aguiiar, alli sueltan las rriendas;
a la exida de Bivar ovieron la corneia diestra
e entrando a Burgos ovieronla siniestra.
Meçio Mio Cid los ombros e engrameo la tiesta:
«¡Albricia, Albar Fañez, ca echados somos de tierra!
»Mas a grand ondra torneremos a Castiella.»

See also