The behemoth is an animal referred to in Job:
Look now at the behemoth which I made along with you; he eats grass like an ox. See now, his strength is in his hips and his power is in his stomach muscles. He moves his tail like a cedar; the sinews of his thighs are tightly knit. His bones are like beams of bronze, his ribs are like bars of iron. He is the first of the ways of God.Job 40: 15-19
Skeptics and some Christians suggest the behemoth is a rhino or elephant, although neither has a tail like a cedar tree. Some creationists believe that the behemoth was a dinosaur, possibly an Apatosaurus (once called the Brontosaurus) or another sauropod.