Jörmungandr, in Germanic mythology, an evil serpent and the chief enemy of Thor. The monstrous serpent was the child of the trickster god Loki and the female giant Angerboda (Angrboda: “Distress Bringer”). During Ragnarök, the final battle between the Norse gods and the forces of chaos, Thor will slay Jörmungandr, only to succumb to the serpent’s poison after striking the fatal blow.