Homeworld of the Migo, usually identified with Pluto, but possibly an as-yet unidentified planet or even another dimension. Byakhee may also dwell here, according to some. It is referenced in The Whisperer in Darkness and The Mine on Yuggoth and is the name (and possibly the destination) of a mission to Pluto in Planetfall on Yuggoth. Given the possible ties between the Migo and Hastur and the possible presence of the Byakhee, who are said to serve Hastur, it is possible that Yuggoth has some unexplained connection with Hastur.
The poem A Chain Gang On Yuggoth takes a less serious look at the world.
In chapter six of Allan and the Sundered Veil, Yuggoth is termed an "idea-colony" within the human mind or soul that is "perceived, variously as a planet, as a god, or as a state of mind" and is served by avatars termed Lloigor, Fruit of Yuggoth or Great Old Ones.