The King of Fighters (KOF) is a series of fighting games by SNK that began with the release of The King of Fighters '94 in 1994. The series was developed originally for SNK's Neo Geo MVS arcade hardware. This served as the main platform for the series until 2004 when SNK retired it in favor of the Atomiswave arcade board. Two King of Fighters games were produced for the Atomiswave platform (The King of Fighters Neowave and The King of Fighters XI) before SNK decided to discontinue using it for the series. The series' most recent arcade hardware is the Taito Type X, first used with the release of The King of Fighters XII. Ports of the arcade games and the original The King of Fighters games have been released for several video game consoles. The latest entry in the series, The King of Fighters XIV, was released for PlayStation 4 and Microsoft Windows in 2016. The next game, The King of Fighters XV, is set to be released in 2022.
The games' story focuses on the title tournament where fighters from multiple SNK games take part. SNK also created original characters to serve as protagonists from each of their story arcs while still interacting with fighters from Art of Fighting and Fatal Fury, among others. Multiple spin-off games, such as the R duology for the Neo Geo Pocket and Maximum Impact for the PlayStation 2, for example, have also been released. There have been multiple cross-over games where the SNK cast interacted with characters created by Capcom, while some characters have been present as guest characters in other games, such as Geese Howard in Tekken 7, Kyo Kusanagi in Fighting Days, and Terry Bogard in Fighting EX Layer and Super Smash Bros. Ultimate.
The King of Fighters was originally conceptualized as a side-scrolling beat 'em up titled Survivor until SNK changed it to a fighting game that took its subtitle from the first Fatal Fury game: Fatal Fury: King of Fighters. Though originally released yearly beginning with the arcade games for the Neo Geo to the video game consoles with The King of Fighters XI, the company decided to take more time to develop their games after 2010. Critical reception of the video games has been generally positive due to their use of teams to fight balancing the gameplay.
SNK released the first game in the series, The King of Fighters '94, on August 25, 1994. It featured characters from SNK's previous fighting game series Fatal Fury and Art of Fighting, as well as original characters (including characters from other franchises such as Ikari Warriors and Psycho Soldier, adapted for a versus fighting game).
The game's success led SNK to release yearly installments for the series numbering the games for the year they were released. The King of Fighters '95, as well as adding new characters, began the series' first story arc titled "The Orochi Saga". It was also the first game in the series that allowed players to create their own three-member teams with any character in the game. The King of Fighters '96 established the second part of "The Orochi Saga". Depending on the playable characters on a team, an exclusive ending would be played. "The Orochi Saga" story arc concluded in The King of Fighters '97. Unlike the series' previous games, The King of Fighters '98 did not feature a story. Instead, it was promoted as a "Dream Match" game that allowed players to choose most of the characters available from the previous titles, including ones that were supposedly dead. SNK refitted the Dreamcast version and renamed it The King of Fighters: Dream Match 1999 with an extended cel animated introduction and 3D backgrounds.
The King of Fighters '99 introduced "The NESTS Chronicles" story arc. In a new tactic, a specific person from a team would be an assistant called a "Striker". This person would be able to aid the team for a few seconds in combat. The Dreamcast version was titled The King of Fighters: Evolution, with several improvements in the game such as new Strikers and better animation. The King of Fighters 2000 is the second part of "The NESTS Saga" as well as the last KOF game produced by SNK before its bankruptcy. It adds a few new playable characters and a couple of Strikers—most from earlier KOF titles and other SNK titles such as Metal Slug and Kizuna Encounter. The King of Fighters 2001 ends the second story arc. The Korean company Eolith helped develop the game after SNK was declared bankrupt. The King of Fighters 2002 was created to reunite old characters from previous KOF games and featured no story, similar to KOF '98. It was also developed by Eolith.
As far as connections with the Dead or Alive series go, Mai Shiranui (originally a Fatal Fury character that has been more well known for her role in The King of Fighters) was added as DLC (no longer available) to Dead or Alive 5 Last Round in 2016, and she returned in 2019 as a DLC for Dead or Alive 6, this time with Kula Diamond from the same series also being added, and unlike the previous game this time they have a very short story segment where they fight Kasumi and Nico respectively. Also, for the mobile game The King of Fighters All Stars, Kasumi, Marie Rose, Honoka and Nyotengu were added as part of a limited time collaboration with Dead or Alive 6, a lower number of characters than other collaborations the mobile game has had, but at the same time they all have 2 costumes, their default one from DOA6 and a more revealing one from the same game.