The Shadow Over Innsmouth is one of the most beloved and eternally chilling stories from H. P. Lovecraft. The narrator travels through the nearby decrepit seaport of Innsmouth which is suggested as a cheaper and potentially interesting next leg of his journey. There he interacts with strange people and observes disturbing events that ultimately lead to horrifying and personal revelations.

It forms part of the Cthulhu Mythos, using its motif of a malign undersea civilization. It references several shared elements of the Mythos, including place-names, mythical creatures and invocations.