Leviathan (Hebrew: לִוְיָתָן, Modern Livyatan, Tiberian Liwyāṯān) is a sea monster referenced in the Tanakh, or the Old Testament.
This word has become synonymous with any large sea monster or creature. In literature (e.g., Herman Melville's Moby-Dick) it refers to great whales, and in Modern Hebrew, it simply means "whale". It is described extensively in Book of Job 41 and mentioned in Job 3:8, Amos 9:3, Psalm 74:13–23, Psalm 104:26 and Isaiah 27:1.
Cirlot identifies the creature as a symbol of the primordial world; monstrous and chaotic, and likens it in this regard to the Scandinavian Midgardorm and Mesopotamian Tiamat.
The Hebrew Leviathan was a development of the earlier Canaanite sea monster Lôtān or Litanu (Ugaritic: Ltn) described as a servant of the sea god Yammu in the Baal Cycle discovered in the ruins of Ugarit. The account has gaps, making it unclear whether some phrases describe him or other monsters at Yammu's disposal such as Tunannu (the Biblical Tannin). Most scholars agree on describing Lôtān as "the fugitive serpent" (bṯn brḥ) but he may or may not be "the wriggling serpent" (bṯn ʿqltn) or "the mighty one with seven heads" (šlyṭ d.šbʿt rašm). Like Yammu's other servants and Yammu himself, Lôtān is defeated by the benevolent storm god Baʿal. His role seems to have been prefigured by the earlier serpent Têmtum whose death at the hands of the benevolent storm god Hadad is depicted in Syrian seals of the 18th–16th century bce.
Sea serpents feature prominently in the mythology of the Ancient Near East. They are attested by the 3rd millennium bce in Sumerian iconography depicting the god Ninurta overcoming a seven-headed serpent. It was common for Near Eastern religions to include a Chaoskampf: a cosmic battle between a sea monster representing the forces of chaos and a creator god or culture hero who imposes order by force. The Babylonian creation myth describes Marduk's defeat of the serpent goddess Tiamat, whose body was used to create the heavens and the earth. As early as 1894, scholars began to note the similarity of these earlier stories and the references to Leviathan's battle with Yahweh found in the Hebrew Scriptures. The mention of the Tannins in the Genesis creation narrative (translated as "great whales" in the King James Version) and Leviathan in the Psalms do not describe them as harmful but as ocean creatures who are part of God's creation. The element of competition between God and the sea monster and the use of Leviathan to describe the powerful enemies of Israel may reflect the influence of the Mesopotamian and Canaanite legends or the contest in Egyptian mythology between the Apep snake and the sun god Horus. Alternatively, the removal of such competition may have reflected an attempt to naturalize Leviathan in a process that demoted it from deity to demon to monster.