In Norse mythology, Jörmungandr is the dragon-like serpent that encircles the world and confronts Thor at Ragnarök.
Jörmungandr, also called the Midgard Serpent, is one of the three monstrous children of Loki and the giantess Angrboða. The other two are the wolf Fenrir and Hel, ruler of the underworld. According to Snorri Sturluson’s Prose Edda, Odin threw the serpent into the sea surrounding Midgard, the human world. It grew until it encircled the entire earth and grasped its own tail.
Thor and Jörmungandr are recurring enemies. In one story, Thor nearly lifts the serpent while disguised by giant magic as a cat. During Ragnarök, Jörmungandr rises from the sea and sprays poison. Thor kills it with his hammer, Mjölnir, but takes only nine steps before dying from the serpent’s venom.
Jörmungandr is not a fire-breathing medieval dragon in the usual European sense. It is primarily a gigantic supernatural serpent, but its world-encircling scale and apocalyptic role make it one of mythology’s most famous dragon-like creatures.