The Megalodon (pronounced /ˡmɛ.gə.ləˌdɒn/ or MEG-a-la-don; meaning "big tooth" or in Greek as μέγας 'οδόντος) was a giant shark that lived in prehistoric times, between about 18 million to 1.5 million years ago and was the apex predator of its time. It is the largest carnivorous fish known to have existed and quite possibly the largest shark to have ever lived. This species is a member of the lamnidae family but its classification is in dispute and a new genus has been proposed. Fossil evidence has revealed that megalodon fed upon large animals, including the early whales.

Some cryptozoologists argue that this shark might still be alive today, probably living in deep waters, and often cite the examples of Coelacanth and megamouth shark to support their claims. However, such beliefs have earned no credibility in the scientific main stream. Megalodon was about 3 times the size of a great white shark living today and enough power to bite a small ship in 2 pieces.