The Ghostly Galaxy is an area in the Wii video game Super Mario Galaxy. Mario will find this area in the Observatory's kitchen, and it can be accessed if he has 20 Power Stars in his possession, including the Grand Stars from the Gateway Galaxy, Bowser Jr.'s Robot Reactor, and Bowser's Star Reactor. As its name implies, this is the haunted location in the game, and thus features plenty of undead species and characters such as Boos and the dreadful Bouldergeist, the boss of the area.
Mario will venture through this level not only to search for power stars, but to also find his lost brother Luigi. Once he does, the green-clad hero will give Mario a Star, and the two will head back to the Comet Observatory. Mario will also come into possession of, for the first time, the Boo suit, which will ultimately turn him into a Boo. It is one of the few galaxies which has Boo mushrooms.
- Luigi and the Haunted Mansion: Mario must navigate his way through the Galaxy's haunted mansion to find Luigi after the latter loses his way in the mansion.
- A Very Spooky Sprint: Mario and the Spooky Speedster race for the Power Star at the end of a spooky racetrack.
- Beware of Bouldergeist: Mario makes his way to the gravestone area where Bouldergeist makes his lair.
- Bouldergeist's Daredevil Run: Mario and Bouldergeist square off again, but there's a catch: Mario must not take damage!
- Purple Coins in the Bone Pen: Mario hunts for purple coins in the Bone Pen near the raceway.
- Matter Splatter Mansion: Mario explores a mansion whose matter can only be touched via Matter Splatter Bubbles!