At the Mountains of Madness is a novella-length story by horror writer H. P. Lovecraft that is considered by Lovecraft scholar S. T. Joshi to represent the decisive "demythology" of the Cthulhu Mythos.

The story was originally serialized in Astounding Stories during 1936. It has been reproduced in numerous collections since Lovecraft's death.

The novella is written from the first-person view of a scholar from Lovecraft's invented Miskatonic University. On an expedition to Antarctica, the narrator's colleagues discover what at first appears to be the remains of an ancient and intelligent race. However, through a series of dark revelations, violence, misunderstandings and insanity-producing events, the narrator learns of Earth's secret history and legacy.

Significance

According to S. T. Joshi, who included this novella as the central story in the first volume of his Annotated Lovecraft series, Mountains reveals Lovecraft's true feelings on the so-called Cthulhu Mythos that subsequent writers attributed to him, and "demythologizes" much of his earlier work.

Many of Lovecraft's stories involve features that appear to be supernatural, such as monsters and the occult. This is interesting, considering that Lovecraft was an atheist and materialist who had no belief in anything supernatural. However, Mountains appears to explain the origins of such elements - from occult symbols to "gods" such as Cthulhu - in rational terms. Mountains explains many elements of the "Cthulhu Mythos" in terms of early alien civilizations that took root on Earth long before humans appeared.