- This article describes Subspace in general. For the actual stages, see Subspace (Part I) and Subspace (Part II).
Subspace (亜空間 Subspace) is a realm central to the plot line of the Subspace Emissary. The realm's general appearance is a mottled, purple-black sky with very little ground (which is also mostly purple), as lightning laces the sky.
Subspace is enforced on the World of Trophies by Tabuu. Over the course of the Subspace Emissary, Subspace Bombs are used to remove portions of the world, drag them into Subspace, and leave a patch of Subspace behind. While inactive trophies and plant life survive the subspacial explosion, it is likely fatal to any living creature, based on how nearby R.O.B.s are torn apart. Once the initial Subspace Bomb detonation is complete, Subspace can be entered by simply walking in these "subspacial bubbles".
Once a piece of the world has been shunted into Subspace, it floats around as a "colony". The colonies are then shut off from the rest of the world, Subspace and otherwise, unless a connection is made between the colony and either Subspace or another colony. Tabuu used the many pieces of the world he collected to create The Great Maze.
- Despite sharing a name with the Subspace of Super Mario Bros. 2, this Subspace is unrelated. However, it is visually and thematically very similar to The Void of Super Paper Mario.
- Subspace also shares, perhaps coincidentally, several similarities with the Void from Final Fantasy V: both are controlled by the main villain, in both cases consumed regions appear in the outside world like large spheres of darkness, and the last area of both is a combination of several absorbed areas from earlier in the game and features many boss fights.