Yuggoth is a planet located at the very edge of the Earth's Solar System in either the Kuiper Belt, Scattered Disk or even as far away as the Oort Cloud. It is the site of a Mi-Go colony, a race of fungoid, crustacean-like extraterrestrials.
- Yuggoth is a major stopping-off point for the Great Old Ones on their way to Earth.
- Yuggoth has its own mini-solar system including Zaman, Nithon, the binary planet Thog & Thok and the Ghooric Zone. It orbits at ninety degrees from the plane of the elliptical. It is the natal home of an “Elder Race” of Yuggothians who died out (perhaps due to the cannibalistic habits of Cxaxukluth?) before the planet became an “outpost” of the Mi-Go territory. Relics of the Elder Race exist including, according to The Revelations of Gla'aki, a city of green pyramids, and a pit which might be “the Pit of Shoggoths”. A dark inhospitable world; its surface is ravaged by high winds, while its "seas" and "rivers" consist of a warm, oily substance which flows sluggishly under basalt bridges. Cities, towers and mines exist on both land and sea.
- Yuggoth has been suggested to be Pluto.
- Na'morha is a named city on Yuggoth.
- The artifact known as the Shining Trapezohedron is stated to have been created on Yuggoth. The Black Seal of Iraan also comes from Yuggoth (HPL: The Haunter of the Dark).
- The Raandeese, according to Les Enfants du Poisson, sometimes travel via a gate known as "The Threshold of Yuggoth", suggesting that they may have been on Yuggoth at some stage too (EXP: "From the Deep and Beyond" [Gregory Nicoll]).
- Several Great Old Ones settled on Yuggoth at one time or another Including: Rhan-Tegoth, Tsathoggua, Ghizghuth, Zstylzhemgni, Hziulquoigmnzhah and possibly Gla'aki.
- If Yuggoth is indeed Pluto it would presumably share Pluto's location in the Kuiper Belt. Pluto was the only Kuiper Belt Object to be discovered during Lovecraft's lifetime; The next KBO would not be discovered until 1992.
- This world bears a similarity to Unicron from the Transformers universe.
- Russell's Guide interprets Yuggoth as a purely mechanical planet.