Cthulhu is a fictional cosmic entity who first appeared in the short story "The Call of Cthulhu", published in the pulp magazine Weird Tales in 1928. The character was created by writer H. P. Lovecraft.

H. P. Lovecraft's initial short story, "The Call of Cthulhu", was published in Weird Tales in 1928 and established the character as a malevolent entity trapped in an underwater city in the South Pacific called R'lyeh. Described as being "...an octopus, a dragon, and a human caricature.... A pulpy, tentacled head surmounted a grotesque scaly body with rudimentary wings", and "a mountain walked or stumbled", the imprisoned Cthulhu is apparently the source of constant anxiety for mankind at a subconscious level, and also the subject of worship by a number of religions (located in New Zealand, Greenland, Louisiana, and the Chinese mountains) and other Lovecraftian monsters (called Deep Ones and Mi-Go). The short story asserts the premise that, while currently trapped, Cthulhu will eventually return, with worshipers often repeating the phrase Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn: "In his house at R'lyeh, dead Cthulhu waits dreaming."