Unaussprechlichen Kulten (the name was supposed to mean "nameless cults" in German, but really translates as "unspeakable/unutterable cults") is a fictitious book, said to be written by Friedrich von Junzt. It is also sometimes called "The Black Book". The full title is actually "Von Unaussprechlichen Kulten" ("Of Unspeakable Cults"); without the preposition, the German dative case would make no sense, as "Unspeakable Cults" would translate as "Unaussprechliche Kulte" (in the nominative). In religion and sociology, a cult is a group of people (often a new religious movement) devoted to beliefs and goals which may be contradictory to those held by the majority of society. ... Friedrich von Junzt is a fictional character in the works of H. P. Lovecraft. ...

The first mention of the book occurs in Robert E. Howard's story "The Children of the Night" as Nameless Cults. H. P. Lovecraft then tried to find a German name for it, and August Derleth finally came up with Unaussprechlichen Kulten, although the German is not a direct translation. Like the Necronomicon, it is mentioned in several stories from Lovecraft's Cthulhu Mythos line. (A German translation of "Nameless Cults", for the curious, would be "Namenlose Kulte.") Robert Ervin Howard (January 22, 1906 – June 11, 1936) was a writer of fantasy and historical adventure pulp stories, published primarily in Weird Tales magazine in the 1930s. ... H. P. Lovecraft Howard Phillips Lovecraft (August 20, 1890 – March 15, 1937) was an American author of fantasy and horror fiction, noted for giving horror stories a science fiction framework. ... August William Derleth (February 24, 1909 – July 4, 1971) was an American writer and anthologist. ... The Necronomicon (Greek: Νεκρονομικόν) is a fictional book of magic, invented by H. P. Lovecraft and frequently featured in his Cthulhu mythos tales. ... Cthulhu Cthulhu mythos is the term coined by the writer August Derleth to describe the shared themes, characters, and elements in the works of H.P. Lovecraft, his protegés, and writers influenced by him. ...