Xoth (or Zoth) is the green binary star where Cthulhu and his ilk once lived before coming to earth. According to the Xothic legend cycle, it is where Cthulhu mated with Idh-yaa to beget Ghatanothoa, Ythogtha, and Zoth-Ommog. It is said to be part of a cluster of stars that includes Abbith, Ymar, and Zaoth.
Xoth is also the native home of Ycnágnnisssz and Zstylzhemghi, and was the temporary home of the latter's "husband", Ghisguth, and their progeny, the infant Tsathoggua. Tsathoggua later went to live on Yuggoth. Afterward, he fled to Cykranosh to escape Cxaxukluth's cannibalistic eating habits.
Xoth may be the star Sirius, since "Xoth" is similar to "Sothis", the Egyptian name for the star. However, it is more likely that Xoth coincides with the star "Zoth" in Smith's writings.