A werewolf, also known as a lycanthrope, is a mythological or folkloric human with the ability to shapeshift into a wolf or a wolf-man hybrid creature, either purposely, by being bitten by another werewolf, or after being placed under a curse. This transformation is often associated with the appearance of the full moon, as noted by the medieval chronicler Gervase of Tilbury, or Petronius in Greek antiquity.
Werewolves are often attributed superhuman strength and senses, far beyond those of both wolves and men. The werewolf is generally held as a European monster, although its lore spread through the world in later times. Shapeshifters, similar to werewolves but concerned with other animals, are archetypes that appear in mainly myths and folk tales accross the planet.
A distinction is often made between voluntary and involuntary werewolves. The former are generally thought to have made a pact, usually with the Devil, and morph into werewolves at night to indulge in nefarious acts. Involuntary werewolves, on the other hand, are werewolves by an accident of birth or illness. In some cultures, individuals born during a new moon or suffering from epilepsy were considered likely to be werewolves.