Cthulhu is a fictional cosmic entity created by writer H. P. Lovecraft. It was introduced in his short story "The Call of Cthulhu", published by the American pulp magazine Weird Tales in 1928. Considered a Great Old One within the pantheon of Lovecraftian cosmic entities, this creature has since been featured in numerous pop culture references. Lovecraft depicts it as a gigantic entity worshipped by cultists, in the shape of a green octopus, dragon, and a caricature of human form. It is the namesake of the Lovecraft-inspired Cthulhu Mythos. Etymology, spelling, and pronunciation.
https://en.wikipedia.org/wiki/Cthulhu