The Shadow over Innsmouth is a horror novella by American author H. P. Lovecraft, written in Novemberâ€"December 1931. It forms part of the Cthulhu Mythos, using its motif of a malign undersea civilization, and references several shared elements of the Mythos, including place-names, mythical creatures, and invocations. The Shadow over Innsmouth is the only Lovecraft story which was published in book form during his lifetime.