|First appearance||Super Mario Galaxy (2007)|
|Number of Stars||2|
|Missions|| Grand Star Rescue|
Gateway's Purple Coins
Gateway Galaxy is the first galaxy in Super Mario Galaxy. In this galaxy, Mario gains the ability to Star Spin. When Mario collects all of the Grand Stars, the Gateway Galaxy becomes accessible again. The Red Luma in the Comet Observatory who tells Mario he has a secret will tell him to collect all 100 Purple Coins. Once Mario collects all of the Purple Coins a Red Power Star will appear and the Luma will activate Red Stars around the observatory.
Grand Star Rescue
When Mario awakens on this planet, a Star Bunny will challenge him to a game of hide-and-seek. The player will have to follow the bunny until he reaches his two friends, who will run and hide. One is found near a crate, another in a crater, and the last in a Warp Pipe. The player will have to catch them all, and a new structure on the planet will appear. Mario will meet with Rosalina and Luma and gain the Star Spin ability. Mario needs to Star Spin the nearby Launch Star to reach the next planet, which has five Star Chips scattered about. To go to the next planet, Mario will have to grab the Star Chips to make a Launch Star and blast Mario to the next planet. Here, a Luma in a cage tells Mario that one of the Goombas on the planet has the key. The player will have to defeat the Goombas on the planet until one gives up a key. Mario will have to collect the key to free the Luma. The Luma then transforms into a Sling Star, which slings Mario to the next planet. On this planet, Mario must defeat the Grand Goomba near the top of the planet to free the other Luma and enter the Warp Pipe. The inside of the planet is filled with yellow switches and moving electrical walls. A big machine stands in the middle of the room; a Grand Star is inside it. Mario needs to step on all the yellow Flip Switches to turn them blue, which will shut the machine down and reveal the Grand Star.
Gateway's Purple Coins
This Power Star is only accessible after the Garden has been unlocked. When Mario enters the galaxy, Rosalina will meet him and a Red Luma will challenge him to gain one hundred Purple Coins. There are seventy coins on the planet and thirty in the air. Mario must use the new Red Star to transform into Flying Mario to gain the thirty in the air. This is the game's sole Red Power Star, and grabbing it allows the use of the Red Star power-up in the Observatory Grounds.
- This is the only galaxy in the game where you have to flip the Flip Switchs off, instead of on.