A knight-errant (or knight errant and white knight) is a figure of medieval chivalric romance literature. The adjective (meaning "wandering, roving") indicates how the knight-errant would wander the land in search of adventures to prove his chivalric virtues, either in knightly duels (pas d'armes) or in some other pursuit of courtly love.
It is worth stressing that in Europe, knight-errantry existed only in literature, although the literature regularly presented itself deceitfully as historical, as non-fiction. The handful of knights-errant there really were were well-to-do young men inspired to enact what they had read about in romances.
The template of the knight-errant are the heroes of the Round Table of the Arthurian cycle such as Gawain, Lancelot and Percival. The quest par excellence in pursuit of which these knights wander the lands is that of the Holy Grail, such as in Perceval, the Story of the Grail written by Chrétien de Troyes in the 1180s.
Although the character is part of the romance genre as it developed during the late 12th century, the term "knight-errant" itself is younger, for the first time recorded (as knygt erraunt) in the 14th-century poem Sir Gawain and the Green Knight. Knight-errantry tales remain popular with courtly audiences throughout the Late Middle Ages. They are written in Middle French, in Middle English and in Middle German. In the 16th century, the genre becomes highly popular in the Iberian Peninsula, Amadis de Gaula was one of the most successful knight-errantry tales of this period. In Don Quixote (1605), Cervantes burlesqued the romances and their popularity. Tales of knight-errantry then fell out of fashion for two centuries, until they re-emerged in the form of the historical novel in Romanticism.