"Beyond the Wall of Sleep" is a science fiction short story by American writer H. P. Lovecraft, written in 1919 and first published in the amateur publication Pine Cones in October 1919.

[1] A former intern and a worker of a mental hospital relates his experience with Joe Slater, an inmate who died at the facility a few weeks after being confined as a criminally insane murderer.

He describes Slater as a "typical denizen of the Catskill Mountain region, who corresponds exactly with the 'white trash' of the South", for whom "laws and morals are nonexistent" and whose "general mental status is probably below that of any other native American people".

The words were in the voice and couched in the paltry vocabulary of Slater but the onlookers could construe from the inadequate language a vision of: green edifices of light, oceans of space, strange music, and shadowy mountains and valleys.

The thought-message went on to explain that, as light beings within the realm of sleep, humans can experience the vistas of many planes and universes which remain unknown to waking awareness.

Reporting on the New York state police, the article cited a family named Slater or Slahter as representative of the backwards Catskills population.

Jack London's 1906 novel Before Adam, which concerns the concept of hereditary memory, contains the passage, "Nor...did any of my human kind ever break through the wall of my sleep.