Johnny Cage (Jonathan "John" Carlton) is a character in the Mortal Kombat fighting game franchise by Midway Games and NetherRealm Studios. Introduced in the original 1992 game, he is an American action film star with an extensive martial arts background. The series depicts Cage as one of the primary heroes defending Earthrealm from various threats, as well as the comic foil. In the first rebooted timeline, Cage is also the love interest of Special Forces officer Sonya Blade and the father of their daughter Cassie Cage.

Cage is inspired by martial arts star Jean-Claude Van Damme, particularly Van Damme's character, Frank Dux, in the 1988 film Bloodsport. A staple of the franchise, Cage has appeared in various media outside of the games. Reception of the character has been generally positive for his role in the series, character development, gameplay, and Fatality finishing moves.

Original concept sketches for a proposed fighting game by artist John Tobias showed a character called "Michael Grimm, the current box office champion and star of such movies as Dragon's Fist, Dragon's Fist II and the award-winning Sudden Violence." Tobias later described them as "R-rated really schlocky 1980s martial arts films". According to martial artist Daniel Pesina, who portrayed Cage in the original game and the 1993 sequel Mortal Kombat II, Pesina used Iron Fist from the Power Man and Iron Fist comic series as the source of inspiration prior to the team settling on spoofing Van Damme.

Midway Games had hoped to license martial artist and actor Jean-Claude Van Damme for a fighting game that was intended to be modeled after Van Damme's 1988 film Bloodsport. The company created a short demo reel that consisted of film footage of Van Damme inserted into a digital background in order to convince the actor to join the project, an attempt that was unsuccessful. When the game later became Mortal Kombat, the Michael Grimm character was retained as a spoof of Van Damme and renamed Johnny Cage, with Van Damme's split-legged groin punch from Bloodsport consequently included as one of Cage's special moves. Mortal Kombat 1 would later feature a special skin for Cage featuring Van Damme's voice and likeness.

Cage's real name of John Carlton was taken from Midway artist and programmer John Carlton, who worked on the NBA Jam arcade game series. Cage was the first character created for Mortal Kombat, and the test prototype of the original game had just two Cage characters fighting each other. In a 1995 interview with Electronic Gaming Monthly, Tobias said that Cage's Fatality finishing move of punching off his opponent's head was the final one created for the game, before which he was going to simply throw his opponent across the screen.

As a narcissistic Hollywood star, Cage serves as comic foil in contrast to the games' more serious characters like Liu Kang and Raiden, which is embellished in the 2011 Mortal Kombat reboot game with a large chest tattoo of his name. Cage's main role in Mortal Kombat X is as a Special Forces consultant instead of an actor; his design by NetherRealm Studios (formerly Midway Games) was their attempt to define whether or not he had taken his martial arts skills seriously since the aftermath of the 2011 reboot game, and he was outfitted in tactical gear that was designed to fit his fighting style while finding the balance between "serious or stoic" and "too goofy". In Mortal Kombat X, Cage's gameplay style is split into three fighting variations like those of the other playable characters; Prima Games deemed him effective at zoning. A female alternate universe variant of Johnny named Janet Cage appears in Mortal Kombat 1, initially as an NPC during the story mode before being added as a downloadable assist character, or "Kameo Fighter".

Introduced in Mortal Kombat (1992), Johnny Cage is a martial artist and actor who is tricked by the sorcerer Shang Tsung into entering the latter's Mortal Kombat tournament to prove that he does not rely on special effects in his films and improve his marketability. In the sequel Mortal Kombat II (1993), Johnny disappears from the set of his latest film to join Earthrealm's warriors, led by Mortal Kombat champion Liu Kang, in traveling to the otherworldly dimension of Outworld to compete in a second Mortal Kombat and save their world from Outworld tyrant, Shao Kahn.

While Cage does not appear in Mortal Kombat 3 (1995) and Ultimate Mortal Kombat 3, the 1996 compilation title Mortal Kombat Trilogy reveals he was killed by Shao Kahn's forces during the latter's invasion of Earthrealm and Johnny's journey to the afterlife was blocked due to the tyrant fusing Earthrealm with Outworld. Nonetheless, the merger restores Johnny's soul and allows him to help his allies defeat Shao Kahn once more before ascending to heaven. In Mortal Kombat 4 (1997), at Johnny's request, Raiden revives him so he can join his friends in fighting the disgraced former deity Shinnok.