Henry Fuseli - Thor Battling The Midgard Serpent, 1788
"The Midgard Serpent, Midgårdsormen, or World Serpent, is, in Norse mythology, a sea serpent, and the middle child of the giantess Angrboða and the god Loki. According to the Prose Edda, Odin took Loki's three children, Fenrisúlfr, Hel and Jörmungandr. He tossed Jörmungandr into the great ocean that encircles Midgard. The serpent grew so big that he was able to surround the Earth and grasp his own tail. When he lets go the world will end." - quote source

Fuseli previously mentioned here.