A Pure Heart is an item that is needed in Super Paper Mario. The first Pure Heart is given to Mario by Merlon when he first comes to Flipside. The Pure Hearts are needed to unlock doors to other places that have a Pure Heart, and when combined, will create the Purity Heart which is used to combat the Chaos Heart. Pure Hearts are the items to counter Count Bleck's plan to destroy the worlds.
Flipside Pure Heart - Given to Mario by Merlon.
Lineland Pure Heart - Given to Mario by Merlee at a temple after defeating Fracktail.
Gloam Valley Pure Heart - Given to Mario by Merlee after defeating Mimi.
Bitlands Pure Heart - Given to Mario by Tippi after saving her.
Outer Space Pure Heart - "Bestowed" Mario by Squirps after bringing him to the Queen's statue.