Robert the Devil (Latin: Robertus Diabolus) is a legend of medieval origin about a Norman knight who discovers he is the son of Satan. His mother, despairing of heaven's aid in order to obtain a son, had asked for help from the devil. Robert's satanic instincts propel him into a violent and sinful life, but he eventually overcomes them to achieve repentance.
The story originated in France in the 13th century and has since provided the basis for many literary and dramatic works, most notably the Meyerbeer opera Robert le diable.