Planet Doom was a planet located in the Ghost Zone. The planet was legendary amongst treasure seekers, as it was were the fabled Catseye of Doom was to be found. The owner of which would be able to rule the universe.
One of the most prominent locations for fortune hunters on Planet Doom were the aptly named Caves of Doom, in which dangerous Ghost Worms and the Ghost Creeper roamed. It was also home to a hidden statue of the Ancient Cat Goddess of Doom, the rightful and only safe place for the Catseye of Doom.
Although not part of our solar system, the Ghostbusters have a planetary map at Ghost Command that points out exactly where Planet Doom is located in the Ghost Zone.
Planet Doom makes it's only appearance in the episode Maze Caves.