Robert the Devil is a legend of medieval origin. Robert is the devil's own child, for his mother, despairing of heaven's aid in order to obtain a son, has addressed herself to the devil.

From the moment of his birth the boy shows his vicious instincts, which urge him, when grown to manhood, to a career of monstrous crime. At last the horror which he inspires everywhere causes him to reflect, and, having found out the awful secret of his birth, he hastens to Rome to confess to the pope. He undergoes the most rigorous penance, living in the disguise of a fool at the emperor's court in Rome. Three times he delivers the city from the assault of the Saracens, but, refusing all reward, he ends his life as a pious hermit. According to another version he marries the emperor's daughter, whose love he has won in his humble disguise, and succeeds to the throne.

The oldest known account of this legend is a Latin prose narrative by a Dominican friar, Etienne de Bourbon (c. 1250). Then it appears in a French metrical romance of the thirteenth century, also in a "dit" of somewhat later date, and in a miracle play of the fourteenth century. A French prose version was also prefixed to the old Croniques de Normandie (probably of the thirteenth century). But the legend owes its popularity to the story-books, of which the earliest known appeared at Lyons in 1496, and again at Paris in 1497, under the title La vie du terrible Robert le dyable. Since the sixteenth century the legend was often printed together with that of Richard sans Peur; it was published in completely recast form in 1769 under the title Histoire de Robert le Diable, duc de Normandie, et de Richard Sans Peur, son fils.

From France the legend spread to Spain, where it was very popular. In England the subject was treated in the metrical romance, Sir Gowther, the work of an unknown minstrel of the fifteenth century. An English translation from the French chap-book was made by Wynkyn de Worde, Caxton's assistant, and published without date under the title Robert deuyll. Another version, not based on the preceding, was written by Thomas Lodge in his book on Robin the Divell (London, 1591). In the Netherlands the romance of Robrecht den Duyvel was put on the index of forbidden books by the Bishop of Antwerp (1621). In Germany the legend never attained much of a vogue; not until the nineteenth century did it pass into the Volksbücher, being introduced by Görres. It was treated in epic form by Victor von Strauss (1854), in dramatic form by Raupach (1835). Meyerbeer's opera Robert le Diable (Paris, 1831) enjoyed great favour for a time. The libretto, written by Scribe and Delavigne, has little in common with the legend except the name of the hero.