God-like alien beings of The Cthulhu Mythos, sometimes said to have rebelled against the Elder Gods. Hastur is sometimes said to be a Great Old One.
In chapter six of Allan and the Sundered Veil, the Lloigor or Fruits of Yuggoth are identified as Great Old Ones with Ithaqqa (Ithaqua) specifically appearing in the story.
An nameless 'Old One' dwells within the moon in The Old One & The Star Spawn.
Outer Gods[]
Some of the beings formerly assumed to be Great Old Ones and Elder Gods are sometimes classed as 'Outer Gods'. The term postdates Lovecraft, although it parallels some of his vague descriptions of the power differences between his creations, but was given backing by the Call of Cthulhu RPG. Great Old Ones are sometimes seen as larval Outer Gods. Often they are similar to the more amoral interpretations of the Elder Gods. They are sometimes associated with the nebulous Other Gods mentioned in connection with Nyarlathotep.