The giant serpent in Norse mythology that encircles the world is known as Jörmungandr, or the Midgard Serpent. It is one of the offspring of the trickster god Loki and represents the cosmic cycle of life and death. Jörmungandr is prophesied to battle the god Thor during Ragnarök, the end of the world, symbolizing the inevitable clash between order and chaos. This mythological figure emphasizes the connection between different realms and the eternal struggle inherent in existence.