The Grandmaster Galaxy is a galaxy in the game Super Mario Galaxy 2. It is the last galaxy to be unlocked in the game and this galaxy is located in World S. This galaxy is unlocked when Mario gets all 120 Power Stars and all 120 secret Green Power Stars, similar to the Grand Finale Galaxy in Super Mario Galaxy. It is an obstacle course with puzzles and enemies. The galaxy is divided into six sections, each presenting a different challenge to the player.
- The first section is where you swing from flower to flower with Yoshi's tongue while avoiding mines, Bullet Bills, and Paragoombas. Choppahs replace the Paragoombas in the galaxy's comet mission.
- The second section is a square of flipswitches. The player must activate them all before the Launch Star appears while avoiding Sentry Beam attacks.
- The third section is a maze of electric bolts that the player must maneuver around via Cloud Flower. The player will have to let go of Yoshi in this part if he/she has not already done so.
- The fourth section you will have to navigate through a path of flip panels while dodging laser waves and coconuts and flaming coconuts.
- The fifth one contains pull stars which you will have to use to navigate through electrical fences, Paragoombas, and mines.
- The sixth and final one if it is the non-daredevil run will have a bunch of Hammer Bros and you will have to defeat them in order to earn the star or move on.
- the seventh section is only playable if you are playing the daredevil run. Here there is nothing else to do but talk to Rosalina and get the star.
This galaxy contains two Stars: one for completing the level and another one for doing it again under Daredevil Comet conditions. In the latter case Mario gets the Star from Rosalina. They should be the 241st and 242nd stars in the game. After you have gotten the star in the daredevil comet run Rosalina will come aboard Starship Mario.
- The place where Rosalina is at the end of the daredevil run greatly resembles the Gate Planet in Super Mario Galaxy.
- This is the only galaxy with no Green Stars in it.
- This is the only galaxy whose Daredevil comet mission has jolly music. In this case, music from Super Mario Galaxy is played throughout the Daredevil level, such as the themes of Gusty Garden Galaxy, Good Egg Galaxy, Bowser's Galaxy Reactor, and the Comet Observatory.
- This is the only galaxy in Super Mario Galaxy 2 that requires the player to collect Star Bits in addition to collecting the Comet Medal for a Prankster Comet to appear.
- The three figures from the Shiverburn Galaxy can be seen in the Pull Star Area.