Azathoth (nicknames: the Daemon Sultan, Seething Nuclear Chaos) is a fictional character, a godlike being referred to in the Weird Tales short stories of H. P. Lovecraft. It is described as both blind and idiotic and is generally considered to be head of the Cthulhu Mythos pantheon:

"That last amorphous blight of nethermost confusion which blasphemes and bubbles at the center of all infinity - the boundless daemon sultan Azathoth, whose name no lips dare speak aloud, and who gnaws hungrily in inconceivable, unlighted chambers beyond amidst the muffled, maddening beating of vile drums and the thin monotonous whine of accursed flutes." — H. P. Lovecraft, The Dream-Quest of Unknown Kadath

"I started with loathing when told of the monstrous nuclear chaos beyond angled space which the Necronomicon had mercifully cloaked under the name of Azathoth." — H. P. Lovecraft, "The Whisperer in Darkness"

"Eventually there had been a hint of vast, leaping shadows, of a monstrous, half-acoustic pulsing, and of the thin, monotonous piping of an unseen flute – but that was all. Gilman decided he had picked up that last conception from what he had read in the Necronomicon about the mindless entity Azathoth, which rules all time and space from a curiously environed black throne at the centre of Chaos." — H. P. Lovecraft, "The Dreams in the Witch House"

Holding court at the centre of the universe, Azathoth is attended by the Outer God Nyarlathotep, who immediately fulfills his almost random urges, and a collection of creatures known simply as Servitors of the Outer Gods. Azathoth is often also referred to as the "nuclear chaos" throughout Lovecraft's Cthulhu Mythos stories. However, whether the author employed "nuclear" to mean radioactive energy, or simply to say that Azathoth is at the centre of things, is unclear.

There are few who directly worship Azathoth, and those who do are usually criminally insane; summoning Azathoth is possible, but will almost certainly bring disaster and doom to those who do so. Thomas Ligotti's "The Sect of the Idiot" mentions a portion of the cult whose nature is not human, composed of identical, wizened, hideous creatures who are under the direct control of the Blind Idiot God himself, and in turn manipulate humanity from the highest room of an abandoned room in a small, unnamed town.

Azathoth has several avatars:

• The Madness from the Vaults
• Xada-Hgla