- “This place... It looks like it might be pretty well protected. I betcha we're moving right in on the enemy's home base. Whaddya say we drop in unannounced?”
- —Lubba, Super Mario Galaxy 2
World 5: Trial of the Galaxies is the fifth world featured in Super Mario Galaxy 2. World 5 is a galaxy cluster. It holds seven galaxies, the last of which, Bowser Jr.'s Boom Bunker, features the third and last encounter with Bowser Jr., who now attacks with his Boomsday Machine.
Galaxies
| Galaxy | Description | Star(s) | Unlocking criterion |
|---|---|---|---|
 Space Storm Galaxy |
This level revolves around mechanical objects and is somewhat based off the Dreadnought Galaxy and the Buoy Base Galaxy from Super Mario Galaxy. The galaxy has an abandoned rocketship-like object and a tower shaped like a Topman similar to Buoy Base Galaxy. Switches that slow down time first appear here. |  
|
Defeat Bowser in Bowser's Gravity Gauntlet. |
 Slipsand Galaxy |
This level is desert-themed and features desert objects such as cacti. Sand Rivers and fireballs are the main obstacles in the level. A pyramid can be seen in the background, but serves no special purpose. | 
|
Get the first Star from Space Storm Galaxy. |
 Shiverburn Galaxy |
This galaxy is similar to the Freezeflame Galaxy from Super Mario Galaxy, as it revolves around the elements of fire and ice. Octoombas and Elite Octoombas are common enemies here. |
|
Get the first Star from Space Storm Galaxy. |
 Boo Moon Galaxy |
This galaxy is stereotypical haunted mansion-themed. The level has poison that will make Mario or Luigi lose a life instantly. Snake Blocks are found throughout the level. This is the only galaxy to involve use of the Boo Mushroom. Common enemies include Octoboos and Boos. |
|
Get the first Star from Space Storm Galaxy. |
 Upside Dizzy Galaxy |
This galaxy is similar to the Rightside Down Galaxy. This galaxy features heavy use of shifts in gravity. The direction of the gravity in this level can change depending on the direction of the arrows that are seen in the background. Paragoombas are frequent enemies in this galaxy. |
|
Get the first Star from Space Storm Galaxy. |
 Fleet Glide Galaxy |
This level features many mechanical parts and takes place on a rocket ship. Like the Wild Glide Galaxy, this galaxy involves Fluzzard Gliding . Enemies here include Magmaarghs and Bats. Many Balloons also appear scattered at different points throughout the galaxy. |
|
Get the first Star from Space Storm Galaxy, then feed the Hungry Luma on the World 5 map 1500 Star Bits. |
 Bowser Jr.'s Boom Bunker |
Bowser Jr. is fought here, seen in the cockpit of the Boomsday Machine. The main enemies here are Boomerang Bros. and Floating Mines. | 
|
Get 55 Stars, including the first one from Space Storm Galaxy. |
Gallery
World 5 as viewed from the Grand World Map
The World 5 pathway
Names in other languages
| Language | Name | Meaning |
|---|---|---|
| Japanese | しれんの銀河 ワールド５ Shiren no Ginga Wārudo 5 |
The Galaxy of Trials: World 5 |
| Chinese | 銀河考驗 World 5 Yínhé Kǎoyàn World 5 |
Galaxy Trials: World 5 |
| Italian | Mondo 5: La Sfida all'Infinito |
World 5: Challenge to Infinity |
| Spanish | Mundo 5: El Desafío Galáctico |
World 5: The Galactic Challenge |
Trivia
- This is the only world in the game where Yoshi does not appear in any galaxy.
- This is the only world in the game where there are no Purple Coin missions.