In biblical mythology, Leviathan is the sea monster described in the Book of Job as powerful and untamable.
Job 41 gives Leviathan an extended description, emphasizing its enormous strength, armored body, fearsome teeth, and apparent immunity to ordinary weapons. The passage presents the creature as something no human can capture or control, reinforcing the contrast between human limitations and divine power.
The name comes from the Hebrew word לִוְיָתָן, commonly transliterated as Livyatan. Other biblical passages associate Leviathan with the sea and with forces that only God can defeat. Later Jewish and Christian traditions developed the creature into a more explicit primordial sea dragon or cosmic adversary.
Leviathan is often confused with Behemoth, another great creature mentioned in Job, but Behemoth is portrayed as a land animal. In later literature, Leviathan also became associated with Satan, although that identification is not the main description in Job.