3-Up Moons are moon-like items that appear in Super Mario World, New Super Mario Bros. U, and New Super Luigi U. They are shaped like crescent moons, have eyes, and can be found on the ground; however, they are extremely rare, with only seven appearing in the entire game (one in each normal world). They have a similar effect as 1-Up Mushrooms; however they give Mario or Luigi three extra lives instead of one. Also, they can only be collected once; if the player replays the level, the moon will disappear from where it was.
In Mario Family, interestingly, there is a sewing design of this item in the game.
In Japan, players could scan the Blue Switch e-Reader card, and obtain 3-Up Moons in Super Mario Advance 4: Super Mario Bros. 3.