The Deep Ones are creatures in the Cthulhu Mythos of H.P. Lovecraft.

They made their debut in Lovecraft's 1931 novella "The Shadow Over Innsmouth". They are described as being an ocean dwelling race, as evidenced by their name, with an affinity for mating with humans.

They entered a contract with the people of Innsmouth to keep the fish plentiful in their area. They also seem to have a supply of gold artifacts of unearthly design. The Deep Ones revere Dagon and his consort Hydra, worshipping them under the names Father Dagon and Mother Hydra.