Dimension D is a location in which you battle Dimentio in Super Paper Mario. It is a small, green dimension that Dimentio created. It is meant to be unescapable and multiply Dimentio's powers 256 fold. When Mario encounters Dimentio at the top of the huge tree in The Bitlands, Dimentio sends himself and the heroes to this dimension. Though his powers are supposed to be multiplied by 256, Dimentio does not realize that this also does the same to Mario's and his Partner's powers. Thus, the battle ensues normally. Later, in the Floro Caverns, Mario must face O'Cabbage in this realm. Near the end of the game, Dimentio sends Count Bleck, Nastasia, and Tippi to Dimension D in hopes of trapping them. They all escape later, however.
- The fact that Dimentio's power is multiplied 256 fold could be a reference to the Wii's 256 bit computing power, the 256-color scheme used in all paper mario games, or even the fact that the number of catch cards available is 256.
- Despite Dimentio's power multiplied by 256, anyone else in the dimension also gets a strength increase.