Super Smash Bros. is a series of platform fighting video games published by Nintendo. Created by Masahiro Sakurai, the Super Smash Bros. series is a crossover featuring many characters from other video game series created by Nintendo and other developers. Its gameplay is distinct from traditional fighting games, with players aiming to knock each other off of stages after accumulating damage with numerous attacks. The games have also featured a variety of side modes, including single-player story modes.

Sakurai conceived the idea of Super Smash Bros. while working at HAL Laboratory in 1998 with the help of Satoru Iwata. The series's first game, Super Smash Bros. (1999), was released for the Nintendo 64 and used characters from Nintendo franchises including Mario, Donkey Kong, The Legend of Zelda, Kirby, and Pokémon. The game was a success, and Sakurai was asked to make a sequel for the then-upcoming GameCube, Super Smash Bros. Melee, which was developed in 13 months and released in 2001.

After Sakurai left HAL Laboratory, Iwata, who had become Nintendo's president, convinced him to continue directing the series. Sakurai directed Super Smash Bros. Brawl (2008) for the Wii and Super Smash Bros. for Nintendo 3DS and Wii U (2014) for the Nintendo 3DS and Wii U. The series's most recent game, Super Smash Bros. Ultimate, was released in 2018 for the Nintendo Switch, with Sakurai again returning as director and Bandai Namco Studios aiding Sora Ltd., Sakurai's own company, in the game's development.

The Super Smash Bros. games have received critical acclaim and commercial success, with the series selling over 77 million units combined as of 2025^[update] and multiple of its games being considered among the best of all time. The series has also attracted a dedicated community of competitive players who compete in esports tournaments, and Super Smash Bros. has inspired numerous other platform fighting games and has been credited for bringing popularity to several of the franchises whose characters it features.

After developing Kirby Super Star (1996), Masahiro Sakurai, a game developer at HAL Laboratory, wished to experiment with 3D graphics and animation following the release of the Nintendo 64 video game console. Sakurai proposed two games to Nintendo for release on the system: a four-player free-for-all fighting game and a RC robot stealth exploration game where the player progressed through levels by hacking into security cameras. While both proposals were praised by Nintendo, HAL Laboratory was currently developing several other games for the Nintendo 64, including Mother 3, and was unable begin full development on either prototype. After HAL's other projects were cancelled, however, the company needed to produce a finished game as soon as possible. The fighting game prototype was chosen as the studio's next project after Sakurai determined it would take less time to complete than the RC game.

The fighting game prototype, titled Dragon King: The Fighting Game, was developed by three people: Sakurai was responsible for the game's planning, design, graphics, modeling, and animation, while his coworker Satoru Iwata handled the programming and a third developer was responsible for the game's audio. Because he was leading another project at the time, Iwata created Dragon King's programming on weekends. Iwata had agreed to the project because he wished to create a four-player game utilizing the three-dimensional joystick on the Nintendo 64 controller, while Sakurai wished to create an alternative to the fighting games dominating the video game industry at the time.

Sakurai had developed the idea for a new type of fighting game in 1996, because he felt that existing fighting games had become too complex, with gameplay over-reliant on combos that reduced the importance of player strategy. He sought to create a game that allowed for more player improvisation and interplay, creating a system of accumulated damage to force players to react differently to each attack instead of making the depletion of the other player's life bar the only goal. He created "smash attacks" that could be triggered with a more aggressive "flick" of the joystick while searching for ways to best integrate the Nintendo 64 controller's joystick into the prototype's gameplay.

While Dragon King had largely the same gameplay as what would become Super Smash Bros., it lacked any crossover elements. Sakurai had reservations about including a cast of original characters, saying that existing fighting games had too many "main characters" competing to be the focus of marketing, making it more difficult for players to care compared to games that have fewer protagonists and several side characters. While Sakurai said that would be acceptable in fighting games released for arcades, the transition to home consoles meant that it was important to establish the game world's "atmosphere" as soon as possible, and he did not want new players to encounter a large roster of unfamiliar characters. Therefore, he asked Nintendo's permission to use various characters from its other games. The proposal to use pre-existing characters was controversial, and Nintendo's Shigeru Miyamoto rejected the idea. In response, Sakurai and Iwata created a demo of the game featuring Mario, Fox McCloud, Samus Aran, and Donkey Kong, and ensured that it was well-balanced before presenting it again. Upon seeing the revised demo, Miyamoto gave permission for the game to use Nintendo characters.