In Jewish legend the Leviathan is an unconquerable monster that lives in the sea. It is usually paired with the Behemoth, another monster that lives in a desert east of the Garden of Eden (some sources say it lives in the mountains). They were created at the same time, but were separated because no one place would be enough for both. At the end of time there will be a battle between the two monsters, and God will slay them both with a sword and the elect will eat them. The Leviathan does not appear in bestiaries, but it is found in some medieval encyclopedias.

The leviathan is usually illustrated as a fire breathing sea dragon, being ridden by the Antichrist.