Dragon King: The Fighting Game (格闘ゲーム竜王, Fighting Game Dragon King) was an unfinished, low-budget fighting game primarily developed by Masahiro Sakurai and Satoru Iwata that was intended for release on the Nintendo 64.

Dragon King: The Fighting Game was supposed be the first installment in a planned series of fighting video games for the Nintendo 64, with the game also being designed to make unique use of the joystick on the controller; unlike other games which took advantage of the analogue stick, like Super Mario 64 or The Legend of Zelda: Ocarina of Time, Sakurai wanted to see how he could use it in a multiplayer environment. Sakurai was also interested in creating a fighting game experience that involved four players fighting at once, instead of the standard one-on-one format seen in most of the era's fighting games. During preliminary development for the game, however, Sakurai felt that the game lacked the appropriate atmosphere for a fighting game on a home console, stating that the characters he had planned for inclusion in the game seemed too similar to one another; while he thought this would be acceptable in an arcade setting, he felt that games for home consoles would need better depth in order to captivate its audience. As a result, Sakurai scrapped most of the original concepts for the game and instead added elements from multiple existing Nintendo franchises. The game was ultimately retooled into Super Smash Bros., which became an unexpected success; the game later spawned a successful series of games, with multiple new installments having since been released.

Little is known about Dragon King's gameplay or design, and all information known about the game comes from interviews and a handful of images shown when the game was in an alpha stage. No gameplay footage has been demonstrated, and a working prototype has not been made publicly available. Images of the game, however, show that much of the core gameplay was similar to Super Smash Bros., with these images featuring damage percents, arenas with platforms, and combatants that do not strictly have to face one another. The tall, thin build of the unnamed fighters and their kicking and punching techniques are also relatively similar to that of Captain Falcon. The background of the stage featured in the screenshots is a photo taken by Satoru Iwata of a Ryūō-chō neighborhood in Yamanashi, Japan, which is where HAL Laboratory's headquarters are based. Before the game was given a title, it was codenamed "Ryūō" after Ryūō-chō, which itself means "Dragon King."