Rainbow Star (レインボースター Reinbō Sutā?), also referred to as Bubble World (バブルワールド Baburu Wārudo?), Bubbleluna (バブルア Baburua?), Rainbow Land (レインボーランド Reinbō Rando?), and Motherland (マザーランド Mazārando?), is the home planet of Bub and Bob, and the main setting for most of the games in the Bubble Bobble series. Rainbow Star is surrounded by numerous other planets, and is part of a large solar system that orbits the star Prominence.
The world itself is based off of Rainbow Islands, and features enemies exclusively from the game throughout its various levels. The Boss of Shadow serves as the boss of the world, solely appearing in his Bubble Dragon form. If the player has not collected three Star Mystery Crests and obtained the giant key, the player will not be able to access the ninth world and will receive the game's bad ending.
- Bubble Bobble Evolution is one of the few games in the series to not take place on Rainbow Star, instead taking place on Earth, specifically in London, England during the 19th Century.
- Likewise, Bubble Bobble 4 Friends also appears to take place somewhere other than Rainbow Star, the events of the game occurring in a child's bedroom full of Bubble Bobble toys that come to life via the light of the moon.