The Four Sword is a weapon used by Link in The Legend of Zelda: the Four Swords series. It is a magical sword that let's it's wielder split themselves into four entities, enabling the multiplayer gameplay found in the Four Swords sub-series. It was originally the Picori Blade, forged by the diminutive, fae-like Minish people. During the events of The Legend of Zelda: The Minish Cap Link gathers the four elements and has the blade reforged into the Four Sword.
When used by Link, it split him into four separate Links of different colors (green, red, blue and purple) representing the elements of wind, fire, water and earth respectively. In The Legend of Zelda: Four Swords Adventures, it is removed from a stone concealing Vaati, releasing him.