Mr. Saturn (known as Dosei-san (どせいさん) in Japan) is a fictional species in the Super Nintendo game EarthBound. They are friendly to the player's party, and help the player defeat the monster Master Belch. All individuals of the species are named Mr. Saturn, except for the friendly Dr. Saturn who will recover all negative status effects for free. They are identical in appearance, each short, pink, with an overlarge nose, whiskers, a bow on its one hair, and no discernible gender. They speak broken English, and erratically use the words "boing," "ding," and "zoom" in their speech for unknown reasons. Also, in-game, the text that appears in the Mr. Saturn text windows is a different font than any other in the game, which can be difficult to read at first.

Mr. Saturns make their home in Saturn Valley, in Eagleland. Their village has round homes which resemble flying saucers and/or the planet Saturn and strange furniture, such as ATMs which bounce up and down in place and resemble Mr. Saturns. Saturn Valley also contains a free hot spring, which will restore all your health and revive fallen party members, and a coffee break that recaps your journey.

Mr. Saturn makes a cameo appearance in Kirby Super Star as one of the treasures in the Great Cave Offensive.

Mr. Saturn also appears in Super Smash Bros. Melee: as a trophy and an object on the battlefield. It will walk about on whatever platform it is on until someone picks it up or it disappears due to inactivity. Mr. Saturn may also be used as a weapon by picking up and throwing him at another character. There is no indication that Mr. Saturn minds being treated like this. Mr. Saturn appears the most in the Onett level from EarthBound.