In Norse mythology

Norse mythology

Norse mythology, a subset of Germanic mythology, is the overall term for the myths, legends and beliefs about supernatural beings of Norse pagans. It flourished prior to the Christianization of Scandinavia, during the Early Middle Ages, and passed into Nordic folklore, with some aspects surviving...

, Jörmungandr , mostly known as Jormungand, or
Jörmungand , or Midgard Serpent , or World Serpent, is a sea serpent

Sea serpent

A sea serpent or sea dragon is a type of sea monster either wholly or partly serpentine.Sightings of sea serpents have been reported for hundreds of years, and continue to be claimed today. Cryptozoologist Bruce Champagne identified more than 1,200 purported sea serpent sightings...

, and the middle child of the giantess Angrboða and the god Loki

Loki

In Norse mythology, Loki or Loke is a god or jötunn . Loki is the son of Fárbauti and Laufey, and the brother of Helblindi and Býleistr. By the jötunn Angrboða, Loki is the father of Hel, the wolf Fenrir, and the world serpent Jörmungandr. By his wife Sigyn, Loki is the father of Nari or Narfi...

. According to the Prose Edda

Prose Edda

The Prose Edda, also known as the Younger Edda, Snorri's Edda or simply Edda, is an Icelandic collection of four sections interspersed with excerpts from earlier skaldic and Eddic poetry containing tales from Nordic mythology...

, Odin

Odin

Odin is a major god in Norse mythology and the ruler of Asgard. Homologous with the Anglo-Saxon "Wōden" and the Old High German "Wotan", the name is descended from Proto-Germanic "*Wodanaz" or "*Wōđanaz"....

 took Loki

Loki

In Norse mythology, Loki or Loke is a god or jötunn . Loki is the son of Fárbauti and Laufey, and the brother of Helblindi and Býleistr. By the jötunn Angrboða, Loki is the father of Hel, the wolf Fenrir, and the world serpent Jörmungandr. By his wife Sigyn, Loki is the father of Nari or Narfi...

's three children, Fenrisúlfr, Hel

Hel (being)

In Norse mythology, Hel is a being who presides over a realm of the same name, where she receives a portion of the dead. Hel is attested in the Poetic Edda, compiled in the 13th century from earlier traditional sources, and the Prose Edda, written in the 13th century by Snorri Sturluson...

 and Jörmungandr, and tossed Jörmungandr into the great ocean that encircles Midgard

Midgard

Midgard is one of the Nine Worlds and is an old Germanic name for our world and is the home of Humans, with the literal meaning "middle enclosure".-Etymology:...

. The serpent grew so large that he was able to surround the Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 and grasp his own tail.