"The Mound" is a horror novella by H. P. Lovecraft, written as a ghostwriting project for Zealia Bishop. It is often considered part of the Cthulhu Mythos due to its themes of ancient, hidden civilizations, cosmic horror, and connections to Lovecraft's broader mythos.

The story follows an unnamed narrator investigating a mysterious burial mound in Oklahoma, where local legends speak of ghostly apparitions and strange disappearances. He discovers a manuscript written by a Spanish explorer, Pánfilo de Zamacona, who in the 16th century found an underground civilization beneath the mound. This lost realm, K'n-yan, is an advanced but decadent society of immortal beings who wield incredible scientific and psychic powers.

"The Mound" expands the Cthulhu Mythos by introducing K'n-yan as one of Lovecraft's lost civilizations, echoing the fates of places like R'lyeh or the Plateau of Leng, where remnants of ancient alien presences continue to exert their influence on the world.