The giant serpent fated to battle Thor during Ragnarok in Norse myth is Jörmungandr, also known as the Midgard Serpent. This colossal creature encircles the Earth, holding its tail in its mouth, symbolizing the cyclic nature of existence. The prophecy foretells a dramatic confrontation between Thor and Jörmungandr, embodying the battle between order and chaos. Their clash is integral to the narrative of Ragnarok, marking the end of the world and the subsequent renewal of life. Jörmungandr’s role highlights the intricate connections between the natural and mythical worlds, illustrating enduring themes of fate and duality.