|Relatives||Cthulhu (grandson), Wilbur Whateley(son), The Dunwich abomination(son)|
|Spouse||Shub-Niggurath, Lavinia Whateley|
|Affiliations||Great Old Ones|
|First appearance||The Case of Charles Dexter Ward|
|Created by||H. P. Lovecraft|
"Yog-Sothoth knows the gate. Yog-Sothoth is the gate. Yog-Sothoth is the key and guardian of the gate. Past, present, future, all are one in Yog-Sothoth. He knows where the Old Ones broke through of old, and where They shall break through again. He knows where They have trod earth's fields, and where They still tread them, and why no one can behold Them as They tread."
—H. P. Lovecraft, "The Dunwich Horror"
Yog-Sothoth (The Lurker at the Threshold, The Key and the Gate, The Beyond One, Opener of the Way, The All-in-One and the One-in-All) is a cosmic entity of the Cthulhu Mythos and the Dream Cycle of H. P. Lovecraft. Yog-Sothoth's name was first mentioned in his novella 'The Case of Charles Dexter Ward' (written 1927, first published 1941). It goes on to be the driving force of the short story, The Dunwich Horror in which it fathers twin boys with a human. The being is said to take the form of a conglomeration of glowing bubbles. It is later mentioned in At the Mountains of Madness as being the thing beyond the mountains that even the Elder Things fear. Its parent was the Nameless Mist. It is the parent of Cthulhu, Hastur the Unspeakable and the ancestor of the Voormi. It is also the father of Wilbur Whateley.
It is heavily implied, if not outright stated, that Yog-Sothoth is Omniscient, and is locked outside the universe, meaning He knows and can see all of space-time all at once, that there is no secret hidden from Yog-Sothoth.
Yog-Sothoth has, like many Lovecraftian Gods, many different apperences throughout the various stories of the mythos, by various authors. However, there seems to be the common agreement that Yog-Sothoth is a mass of glowing orbs, with eyes or tendrils in some versions, and in others, simply the orbs.