What is the name of the final boss in the original Super Smash Bros.?

The final boss in the original Super Smash Bros. is Master Hand.

Master Hand appears at the end of the game's single-player mode on Final Destination. Unlike ordinary fighters, he is a floating white glove and cannot be defeated by knocking him off the stage; players must deplete his health instead. His unusual design helped establish Smash Bros. as more than a conventional fighting game.

The opening sequence shows Master Hand arranging toy-like figures of Nintendo characters before bringing them to life, linking him to the game's playful fantasy premise. A common mix-up is Crazy Hand, Master Hand's left-hand counterpart, but Crazy Hand debuted in Super Smash Bros. Melee, not the original game. Tabuu is instead the final boss of Brawl's Subspace Emissary story mode, while Giga Bowser is a later boss encounter.