- “We've sure come a long way, thanks to your efforts! Let's keep this good thing going, am I right? The helm is yours, Captain!”
- —Lubba, Super Mario Galaxy 2
World 4: The Many Mysteries of the Cosmos is the fourth world in Super Mario Galaxy 2. It is located near a spiral galaxy. It holds seven galaxies, the last of which, Bowser's Gravity Gauntlet, features the second encounter with Giant Bowser, who again attacks Mario on a small planet, though now with several new moves. The Hungry Luma galaxy is available right when the player enters, which does not happen in any other world.
Galaxies
| Galaxy | Description | Star(s) | Unlocking criterion |
|---|---|---|---|
 Supermassive Galaxy |
This galaxy depicts many common Mario enemies and elements at an extraordinary size. Some include Piranha Plants, Lumas, coins and Platforms. |   
|
Defeat Bowser Jr. in Bowser Jr.'s Fearsome Fleet. |
 Flipsville Galaxy |
This galaxy is home-themed, with many dollhouse-like planets. The main gimmicks in this galaxy are flipping platforms known as grates, which the player needs to perform a Ground Pound to turn these platforms over and flip the gravity to gain access to different areas. |
|
Get the first Star from either Supermassive Galaxy or Sweet Mystery Galaxy. |
 Starshine Beach Galaxy |
This galaxy is beach-themed and has some elements from the game Super Mario Sunshine's Isle Delfino, including Piantas that can hurl the player to other parts of the galaxy and a statue similar to the Grand Pianta Statue in Delfino Plaza. |
|
Get the first Star from either Flipsville Galaxy or Honeyhop Galaxy. |
 Chompworks Galaxy |
This is the only galaxy to revolve around the use of the Spring Mushroom. Gearmos inhabit the area. Chomps, as the galaxy's name implies, are the most common enemy here, usually blocking the path to a Launch Star. |
|
Get the first Star from either Flipsville Galaxy or Honeyhop Galaxy. |
 Sweet Mystery Galaxy |
This galaxy consists of different types of food and sweets, such as ice cream, pancakes, lollipops, candy canes, pretzels and donuts. Most of the platforms here are invisible and can only be revealed using Bulb Yoshi. Common enemies here include Smeeches and Choppahs. The galaxy entirely revolves around the use of Bulb Berry. |
|
Feed the Hungry Luma on the World 4 map 1200 Star Bits. |
 Honeyhop Galaxy |
This level revolves around the use of the Bee Mushroom. Honeybees are found throughout the level and teach Mario on how to use the Bee Suit. The level also features honey walls, which Mario can traverse as Bee Mario. Queen Bee is also found in this galaxy, as are many Choppahs and Octoguys. |
|
Get a Star from Supermassive Galaxy. |
 Bowser's Gravity Gauntlet |
This level is based almost entirely on gravitational forces. Most of the level involves sidescrolling, except for the beginning and the end. The level is mostly covered in lava, save for a few sections. Magikoopas are common enemies here and can summon Li'l Cinders at will. Fire Bars are placed throughout the whole level, even underwater. Fireballs are also present, and defy gravity because they can change direction in midair. When Mario reaches the end, Bowser will challenge Mario to a battle. | 
|
Get 40 Stars, including the first one from either Starshine Beach Galaxy or Chompworks Galaxy. |
Gallery
World 4 as viewed from the Grand World Map
The World 4 pathway
Names in other languages
| Language | Name | Meaning | Notes |
|---|---|---|---|
| Japanese | ふしぎのせかい ワールド４[?] Fushigi no Sekai Wārudo 4 |
A World of Wonder: World 4 | |
| Chinese | 不可思議的世界 World 4[?] Bùkěsīyì dè Shìjiè World 4 |
A World of Wonder: World 4 | |
| Italian | Mondo 4: Gli Infiniti Misteri del Cosmo[?] | World 4: The Infinite Mysteries of the Cosmos | |
| Spanish | Mundo 4 : En Busca de los Misterios del Cosmos[?] | World 4: In Search of the Mysteries of the Cosmos |