Reynard the Fox is a literary cycle of medieval allegorical Dutch, English, French and German fables. The first extant versions of the cycle date from the second half of the 12th century. The genre was popular throughout the Late Middle Ages, as well as in chapbook form throughout the Early Modern period.

The stories are largely concerned with the main character Reynard, an anthropomorphic red fox and trickster figure. His adventures usually involve his deceiving other anthropomorphic animals for his own advantage, or trying to avoid their retaliatory efforts. His main enemy and victim across the cycle is his uncle, the wolf, Isengrim (or Ysengrim).

While the character of Reynard appears in later works, the core stories were written during the Middle Ages by multiple authors and are often seen as parodies of medieval literature, such as courtly love stories and chansons de geste, as well as a satire of political and religious institutions. The trickster fox, Reynard, lives in a society of other talking animals (lion, bear, wolf, donkey, etc), making the stories a beast epic.

The original copies were written in Old French, and have since been translated into many different languages. However, the tales of Reynard come from all across Europe and each retelling has details that are specific to its area. The tales, no matter where they take place, are designed to represent the society around them and include the structures of society around them, such as a noble court. While the authors take many liberties with the story telling, not all of the satire is meant to be rude or malicious in intent.

The main characters are anthropomorphic animals. The given names of the animals are of Old High German origin. Most of them were in common use as personal names in medieval Lorraine. The characters of Reynard the Fox were based on the medieval hierarchy, and are treated as human throughout the tales. Since multiple authors wrote the text, characters' personalities often change. Throughout the stories, these characters often switch between human and animal form and often without notice.

The characters who switch between human and animal form are often those of elite status, while the characters who don't change tend to be peasants. Often, the readers will find themselves able to empathize with Reynard. They find that the situations he is in are not often that different from their own lives, and this carries across the decades. The common usage of animals as characters in tales has made it so the stories that touch on morally gray areas are easier to understand and accept.

Foxes in general have the reputation of tricksters in traditional European folklore. The specific character of Reynard is thought to have originated in Lorraine folklore, from where it spread to France, Germany, and the Low Countries.^{[need quotation to verify]} Alternatively, a 19th-century edition of a retelling of the Reynard fable states definitively with "no doubt whatever that it is of German origin" and relates a conjecture associating the central character with "a certain Reinard of Lorraine, famous for his vulpine qualities in the ninth century".

Joseph Jacobs, while seeing an origin in Lorraine, traces classical, German, and "ancient northern folk-lore" elements within the Reynard stories. Jacob Grimm in his Reinhart Fuchs (Berlin, 1834) provided evidence for the supposition on etymological grounds that "stories of the Fox and Wolf were known to the Franks as early as the fourth, fifth, and sixth centuries".