Fierabras (from French: fier à bras, "brave/formidable arm") or Ferumbras is a fictional Saracen knight (sometimes of gigantic stature) appearing in several chansons de geste and other material relating to the Matter of France. He is the son of Balan, king of Spain, and is frequently shown in conflict with Roland and the Twelve Peers, especially Oliver, whose prowess he almost rivals. Fierabras eventually converts to Christianity and fights for Charlemagne.
The oldest text of the story of Fierabras is a 12th-century (c. 1170) French chanson de geste of roughly 6,200 alexandrines in assonanced laisses. The story is as follows: the Saracen king Balan and his 15-foot-tall (4.6 m) son Fierabras return to Spain after sacking the church of Saint Peter's in Rome and taking the relics of the passion. Charlemagne invades Spain to recover the relics and sends his knight Olivier de Vienne, Roland's companion, to battle Fierabras.
Once defeated, the giant decides to convert to Christianity and joins Charlemagne's army, but Olivier and several other knights are captured. Floripas, Fierabras' sister, falls in love with one of Charlemagne's knights, Gui de Bourgogne. After a series of adventures, Charlemagne kills king Balan, divides Spain between Fierabras and Gui de Bourgogne (who marries Floripas), and returns to Saint-Denis with the holy relics.
The story was put into prose three times in the 14th and 15th centuries.