The Battle of Bairén is fought between the forces of Rodrigo Díaz de Vivar, also known as "El Cid", in coalition with Peter I of Aragon, against the forces of the Almoravid dynasty, under the command of Muhammad ibn Tasufin.

The battle is part of the long Reconquista of Spain, and results in a victory for the forces of the Kingdom of Aragon and the Kingdom of Valencia.