Raiden (Japanese: 雷電, /ˈreɪdɛn/ RAY-den), is a fictional character in the Mortal Kombat fighting game franchise by Midway Games and NetherRealm Studios. Based on the Japanese deity Raijin, he is depicted as the god of thunder who possesses control over lightning. He debuted in the original 1992 game and has appeared as a playable character in every main installment except Mortal Kombat 3 (1995) and its first update. In the storyline of the games, Raiden is the protector of Earthrealm. He fulfills his duty by selecting and training the warriors who defend Earthrealm from various threats, while also participating directly in the realm's defense. Raiden generally serves as a mentor figure to the franchise's heroes, although he sometimes assumes a darker role in the story, which sees him become more ruthless in his protection of the realm. In Mortal Kombat 1, the new main playable Raiden is depicted as a human who was raised at a farmland and becomes Earthrealm's current Mortal Kombat champion in Liu Kang's timeline, while his previous godly counterpart also exist as a Titan of his own timeline.

One of the franchise's central characters, Raiden has appeared in various related media outside of the Mortal Kombat games, including guest appearances in NBA Jam Tournament Edition (1995), NFL Blitz (1997), Unreal Championship 2 (2005), and Injustice 2 (2017).

The character was inspired by multiple Japanese game designer John Tobias explored in the making of the franchise. However, Raiden's biggest inspiration came from the Western film Big Trouble in Little China. Raiden has generally received a positive reception and is among the series' most popular characters for his design and special abilities. Though his role has been called repetitive, his transformation into a darker counterpart was a welcome change to multiple journalist reviewing the games' narrative.

As designer John Tobias was seeking inspiration for more characters in Mortal Kombat, he visited the Field Museum of Natural History and in their Japanese artifacts display of the Asian antiquities wing, he found a statue of the Raijin, and decided that the game needed a Japanese thunder god. On his research of the Raijin, Tobias decided to take in the deity's alternate spelling of Raiden, and seeing that the traditional Shinto Raijin was usually portrayed as a small, red-skinned demon-like creature that beats a drum to create thunder, opted to employ a different design. Tobias took inspiration from the character Lightning from the film Big Trouble in Little China, a warrior who can conjure lightning and wears a conical hat.

Raiden's name was spelled "Raiden" in all of the original arcade games and in every game since Mortal Kombat 4. However, the PC and console ports released until Mortal Kombat Trilogy, along with both movies and the TV series, changed the name to "Rayden", fearing the original spelling would lead to trademark issues from Seibu Kaihatsu's shoot 'em up game also named Raiden. Ed Boon personally hated that Acclaim spelled it with a Y.

In an interview featured in Deception, Ed Boon said that the hat that actor Carlos Pesina wore to portray the character in the earlier Mortal Kombat games was ruined as a result of Pesina repeatedly performing falls during production.^{[citation needed]} Raiden was voiced by Midway employee Jon Hey in the first two games. He became well known for yelling randomly while performing his "Torpedo" move (aka "the Superman move"). Fans originally believed that he was yelling in Japanese, while others believed it to be mangled English phrases such as "Your momma's from LA", or "Santa Monica!". Tobias revealed that Raiden was merely speaking gibberish and not actual Japanese, as it was originally intended.

Raiden was originally going to use his staff as a weapon already in Mortal Kombat II, but Midway was forced to scrap it due to memory constraints. He was unplayable in Mortal Kombat 3 where he appeared in the attract mode to state that he was forbidden from participating in the game's conflict. He also appeared as part of Nightwolf's Friendship, which saw Nightwolf transform into Raiden alongside a Mortal Kombat II arcade cabinet. The Friendship would include one of two quotes, "I've never seen a Kano transformation", or "No, But I Can Do a Raiden Transformation", both of which were based on false reports that Kano was secretly playable in Mortal Kombat II and Raiden likewise in Mortal Kombat 3. After Raiden became playable in the update Mortal Kombat Trilogy, the Nintendo 64 version changed the Friendship.^{[citation needed]}

In the original Mortal Kombat, Raiden is invited to compete in the titular tournament by its grandmaster sorcerer Shang Tsung. Raiden accepts and takes on a human form to compete. In Mortal Kombat II, watching events unfold from above, Raiden realizes Outworld emperor Shao Kahn's intentions. He warns the surviving members of the original tournament, Liu Kang and Kung Lao, of Shao Kahn's threat before venturing to Outworld. Despite Shao Kahn taking almost every soul on Earth as his own, Raiden was able to protect the souls of Liu Kang and other chosen warriors. Initially unable to participate due to the merger of Outworld and Earthrealm, Raiden sacrifices his immortality in order to help his chances against the Kahn after the Elder Gods refuse to assist him in Mortal Kombat Trilogy.