What serpent encircles the world in Norse myth?

Jörmungandr is the serpent that encircles the world in Norse myth. Also called the Midgard Serpent or World Serpent, it lives in the ocean surrounding Midgard, the human world, and grows so immense that it can coil around the earth and bite its own tail.

According to Snorri Sturluson’s Prose Edda, Jörmungandr is a child of Loki and the giantess Angrboða. Its siblings include Fenrir, the monstrous wolf, and Hel, ruler of the realm of the dead. Odin has the serpent cast into the sea, where its extraordinary size becomes a threat to the cosmic order.

Jörmungandr is Thor’s great enemy. In one famous episode, Thor nearly lifts the disguised serpent while fishing with the giant Hymir. At Ragnarök, the serpent releases its tail and battles Thor. Thor kills it with his hammer, Mjölnir, but retreats only nine steps before dying from the creature’s venom.

Níðhöggr is another serpentlike dragon in Norse mythology, but it gnaws at the roots of Yggdrasil rather than encircling Midgard. Fenrir is a wolf, and Sleipnir is Odin’s horse.