he King of Fighters (ザ・キング・オブ・ファイターズ, Za Kingu obu Faitāzu), officially abbreviated KoF, is the premiere series of fighting games by SNK Playmore, formerly SNK. The series was originally developed for SNK's Neo-Geo MVS arcade hardware, which served as the main platform for the series until 2004, when SNK retired the MVS in favor of the Atomiswave arcade board (which has been recently discarded in favor of an even more advanced arcade system, the Taito Type X2). Ports of the arcade games and original King of Fighters games have been developed for the Neo Geo CD, Neo Geo Pocket, Nintendo Game Boy, Game Boy Advance, Nokia N-Gage, Sega Saturn, Sega Dreamcast, PlayStation, PlayStation 2, PlayStation 3, Xbox, and Xbox 360. Older games in the series have been re-released as part of compilations or given their own special remakes for the Wii, PSP, and PlayStation 2. The King of Fighters XII was released on April 10, 2009. The latest game in the main series, "The King of Fighters XIII" had a preview shown in Akihabara. It was released for the arcades on July 14, 2010 and for consoles on December 1, 2011 in Japan, November 22, 2011 in North America and November 25, 2011 in Europe.The first game in the series, The King of Fighters '94 was released by SNK in 1994. The game was originally designed to be a dream match of characters from the company's various arcade titles, particularly Fatal Fury, Art of Fighting, Ikari Warriors and Psycho Soldier. The success of the game lead to SNK to release yearly installments of the series and numbered the games for the year they were released. However, this naming system posed problems similar to those with sports games named by year: once the new yearly edition debuts, consumers often perceive the previous year's edition as outdated and less desirable to own. In order to combat this, SNK frequently rotates which characters take part in the current year's edition, encouraging fans of omitted characters to buy and play older editions. Additionally, SNK could not always release its console version of the arcade game in the same year for which it was titled. By 2004, SNK abandoned yearly releases of the series and numbered future games in a more traditional manner; the first main series game released as such was The King of Fighters XI.

In 2004, SNK produced the first 3D installment of the series, KOF: Maximum Impact. The game and its two sequels use an alternate story for characters and settings from previous games of the series, leaning more towards the South Town-based series like FF and AoF. The producer of the Maximum Impact series, Falcoon, stated that the Maximum Impact games are in a different canon from the original series of games. The King of Fighters tournament, the namesake of this series, actually originated in Fatal Fury, a classic SNK fighting game that predated the KOF series. Fatal Fury and Art of Fighting also revisited the tournament before SNK released KOF '94.

The King of Fighters games have had a number of villains as their individual end bosses. The first of these was Rugal Bernstein in '94 who had a tendency to submerge his defeated foes in liquid metal, turning them into grisly trophies commemorating his victories. During the Orochi saga, Orochi is introduced as an ominous force from ancient times bent on revenge on those who imprisoned it and was aided by his four heralds. In later games, a mysterious organization called NESTS attempts to kidnap and succeeds in cloning Kyo Kusanagi in hopes of using his power to take over the world. The leader of NESTS, who called himself Igniz, hoped to amass enough power to become a god. Other villains in later games include Mukai and "Those from the past" that he affiliates himself with, including Magaki, as well as the Mephistopheles group (Maximum Impact series).

In order to preserve their characters' images, SNK ceased to age their characters since The King of Fighters '95 and they have remained the same ages since then. This means that characters introduced in The King of Fighters '94 have only aged one year in the series. To stay true to this theme, newer characters following this year also keep the same age they have when introduced. Some concessions to age and the passing of time exist, though, such as Terry's switch to his Garou outfit, or Kyo no longer being in high school since 1998. Ages have stopped being officially listed since KOF XI and KOF XIII.

Kyo Kusanagi: is one of the main protagonist in SNK Playmore's King of Fighters video game series; he was first introduced in The King of Fighters '94 as the leader of the Japan team. He is the rival of Iori Yagami.

He was first introduced as a cocky delinquent high school student who is the heir of his clan, Kusanagi, one of the three clans that sealed the legendary snake entity, Orochi, 1,800 years ago. His clan wields pyrokinetic powers, an inherited power that few members obtain. They, along with the Yasakani and Yata clans, keep one of the three sacred treasures used to contain Orochi long ago. His family's treasure is the Kusanagi-no-Tsurugi (草薙の剣, Kusanagi-no-Tsurugi) or Kusanagi sword and his family crest is the sun, represented in a stylized halo of fire. His official nickname is Scion of the Flame.

Iori Yagami八神 庵, Yagami Iori) is a video game character who made his first appearance in the Neo Geo fighting game, The King of Fighters '95. He is a central recurring character and the initial enemy (and eventual rival) of Kyo Kusanagi.

He is the heir to one of the three clans that sealed the legendary snake entity, Orochi, 1,800 years ago. His clan, formerly known as the Yasakani (八尺瓊, Yasakani), wields pyrokinetic powers. They keep the seal over Orochi intact with help from the Kusanagi and Yata clans using three ancient artifacts. His family's treasure is the Yasakani no Magatama (八尺瓊曲玉, Yasakani no Magatama) and his family crest is the crescent moon, which he wears on the back of his jacket. He also wears a plain silver ring around his left middle finger. The significance of the ring (if any) is unknown. His official nickname is Unbridled Instinct.

Aside from the main body of the King of Fighters series, Iori features his own drama CD and character image album. His character is also a member of SNK's character image band, Band of Fighters and he also appears as a regular antagonist in the spin-off manga, The King of Fighters: Kyo.