Kadath is a fictional mountain in HP Lovecraft's Dreamland. It lies in the vast and perpetually dark boreal desert, known as the Cold Wastes, north of the town of Inquanok, and the hideous Plateau of Leng, and is of pure onyx.

Atop this mountain is a gargantuan castle, also of onyx, in which dwell the minor gods of Dreamland. It is virtually inaccessible to humans, and very, very, very few would care to even attempt to cross the frightful Cold Wastes to reach it in the first place.