Slaves of Sleep is a science fiction novel written by L. Ron Hubbard. It was first published in book form in 1948 by Shasta Publishers; the novel originally appeared in 1939 in an issue of the magazine Unknown. The novel presents a story in which a man travels to a parallel universe ruled by Ifrits. The protagonist takes on the identity of a human in this dimension, and becomes involved in the politics of Ifrits in this fictional world.