Grand Finale Galaxy

The Grand Finale Galaxy is the final galaxy in Super Mario Galaxy. The level takes place in Castle Gardens (also called Toad Town in the guide by Prima Games) from the beginning of the game, with creatures from later parts of the game now attending the Star Festival, including Penguins, Bees, Gearmos, and Star Bunnies, the four major NPC types in the game. The galaxy is unlocked after all 120 Power Stars have been obtained with both Mario and Luigi, and is reached by talking to the fourth Green Luma on the Planet of Trials. This galaxy has the 121st Power Star for both Mario brothers. The Toad Brigade and their ship, the Starshroom, are found outside of the castle. This is the only galaxy not mentioned in the Super Mario Galaxy Prima Games guide. This galaxy also contains the only Purple Coin mission that does not have the words "Purple Coins" in the name. It is also one of the two galaxies to have a Purple Coin mission not triggered by a Prankster Comet, the other one being in the Gateway Galaxy.

After the player has collected all the Purple Coins, the Mailtoad will receive a message. If the player talks to him, he will send a congratulatory picture to the Wii Message Board. This picture differs depending on whether the player spoke to the Mailtoad as Mario or Luigi. If Mario speaks to him, the picture will show Mario and Peach standing on the Starting Planet of the Good Egg Galaxy with some Lumas, including the apricot Luma. If Luigi speaks to the Mailtoad, the picture will feature Luigi and Rosalina standing in front of Peach's Castle with the Toad Brigade. The picture can also be sent to friends. In the Super Mario 3D All-Stars version of Super Mario Galaxy, the "Yes" and "No" prompts are removed and the two images obtained from him are automatically sent to the Nintendo Switch album if the player talks to him. Additionally, the message from the Super Mario Galaxy staff that was originally sent to the Wii Message Board is now read out by the Mailtoad in-game.

On the list of galaxies, this galaxy is simply called "Grand Finale", lacking the "Galaxy" name at the end that all other galaxies on the list have.

Star Festival (Starting Planet)
Toad Town and the exterior of Peach's Castle are shown. The castle and the area around it is based on the design introduced in Super Mario 64, containing a large lake with a river flowing into it, but expanded to include a pathway to Toad Town. The path goes through the town and into the castle.

There is an invisible wall that stops the player from entering the castle itself and the lake. If the wall is bypassed by hacking, the castle and lake have no collision and will cause the player to fall and lose a life.

Mission
This galaxy contains only the following mission.

Trivia

 * It is possible to take damage (and thus lose a life) in this galaxy. The player can simply jump into the fire roasting food that is just past the gate to Peach's castle area near Yellow Toad.
 * Despite Earth seemingly being located underneath the Comet Observatory, this galaxy is accessed in the same way as the three Trial Galaxies, by flying to a distant galaxy in the sky.