Mortal Kombat universe
500 years ago, the annual Shaolin Tournament, long the most prestigious fighting tournament in the world, was interrupted by the appearance of an old sorcerer and a strange four-armed creature, who entered the tournament and defeated the Great Kung Lao. This Shokan warrior was the half-human, half-dragon fighter named Goro, who became the ultimate fighting champion for the next five hundred years. This was all part of Shang Tsung's plan to tip the balance into chaos and help Outworld conquer the Earth Realm. With Outworld already having won nine tournaments in a row, the heroes would have to avoid handing Earth Realm its tenth loss, or all of humanity would crumble into the darkness of the Outworld.
- Liu Kang: Once a member of the super-secret White Lotus Society, Liu Kang left the organization in order to represent the Shaolin temples in the Tournament. Kang is strong in his beliefs and despises Shang Tsung. He enters the Tournament to defeat Shang Tsung and emerge victorious.
- Johnny Cage: A martial arts superstar trained by great masters from around the world, Cage uses his talents on the big screen. He is the current box-office champ and star of such movies as Dragon Fist and Dragon Fist II as well as the award-winning Sudden Violence. He enters the Tournament mostly for fame.
- Kano: Mercenary, thug, extortionist, and thief: Kano lives a life of crime and injustice. He is a devoted member of the Black Dragon, a dangerous group of cut-throat madmen feared and respected throughout all of crime's inner circles. He enters the Tournament for the supposed wealth involved.
- Sonya Blade: Sonya is a member of a top U.S. Special Forces unit and paramilitary police force. Her team was hot on the trail of Kano's Black Dragon organization. They followed them to an uncharted island where they were ambushed by Shang Tsung's personal army. She enters the Tournament to save her comrades and get Kano.
- Raiden: The name Raiden is actually that of a deity known as The Thunder God. It is rumored he received a personal invitation by Shang Tsung himself and took the form of a human to compete in the Tournament. He enters the Tournament solely for competition.
- Sub-Zero: The actual name or identity of this warrior is unknown. However, based on the markings of his uniform, it is believed he belongs to the Lin Kuei, a legendary clan of Chinese ninjas. He enters the Tournament for reasons unknown.
- Scorpion: Scorpion's true name and origin are not known. He has shown from time to time distrust and hatred towards Sub-Zero. Between Ninjas, this is usually a sign of opposing clans. He enters the Tournament to seek revenge.
- Reptile: (green palette swap of Sub-Zero and Scorpion) Shang Tsung's personal protector, Reptile lurks in the shadows stopping all those who would do his master harm. His human form is believed to disguise a horrific reptilian creature whose race was thought extinct millions of years ago. He enters the contest hoping to defeat all and protect his master.
- Goro: Goro became Grand Champion of the Mortal Kombat tournament after defeating the Great Kung Lao. For over 500 years, he has remained undefeated and currently serves Shang Tsung to help Shao Khan, Tsung's master, gain control of Earthrealm.
- Shang Tsung: A powerful and deadly sorcerer, Tsung was a Grand Champion of Mortal Kombat until the Great Kung Lao defeated him. Years later Tsung returned with Goro, a Shokan prince, and entered the Tournament. He had been ordered to by Shao Khan, his master, to win Mortal Kombat in order to weaken the portals between Earthrealm and Outworld so Khan can conquer it. After Goro defeated the Great Kung Lao, the Outworld's domination of Mortal Kombat had begun.
Mortal Kombat II universe
Following his defeat, Shang Tsung begs his master, Shao Kahn, to spare his life. He tells Shao Kahn that the invitation for Mortal Kombat cannot be turned down, and if they hold it in Outworld, the Earthrealm warriors must attend. Kahn agrees to this plan, and restores Tsung's youth. He extends the invitation to Raiden, who gathers his warriors and takes them into Outworld. The tournament is dangerous, as Shao Kahn has the home field advantage, and an Outworld victory will unbalance the furies and allow Outworld to subsume Earthrealm.
- Liu Kang: After winning the Shaolin Tournament from Shang Tsung's clutches Kang returns to his temples. He discovers his sacred home in ruins and his Shaolin brothers killed in a vicious battle with a horde of Outworld warriors. Now he travels into the Dark Realm to seek revenge.
- Johnny Cage: After Shang Tsung's tournament, the martial arts superstar disappeared. He follows Liu Kang into the Outworld, where he will compete in a twisted tournament which holds the balance of earth's existence... as well as a script for another blockbuster movie.
- Raiden: Watching events unfold from high above, the thunder god realises the grim intentions of Shao Kahn. After warning the remaining members of the Shaolin Tournament, Raiden soon disappears. He is believed to have ventured into the Outworld alone.
- Sub-Zero: Thought to have been killed in the Shaolin Tournament, Sub-Zero mysteriously returns. It is believed he traveled into the Outworld to again attempt to assassinate Shang Tsung. To do so he must fight his way through Shao Kahn's tournament.
- Scorpion: The hell-spawned spectre rises from the pits. After learning of Sub-Zero's return, he again stalks the ninja assassin, following him into the dark realm of the Outworld where he continues his own unholy mission.
- Reptile: As Shang Tsung's personal protector, the elusive Reptile lurks in the shadows stopping all those who would do his master harm. His human form is believed to disguise a horrid reptilian creature whose race was thought extinct millions of years ago.
- Shang Tsung: After losing control of the Shaolin Tournament, Tsung promises his ruler Shao Kahn to shape events that will lure the earth warriors to compete in his own contest. Convinced of this plan, Shao Kahn restores Tsung's youth and allows him to live.
- Kung Lao: A former Shaolin Monk and member of the White Lotus society, he is the last descendant of the Great Kung Lao who was defeated by Goro 500 years ago. Realizing the danger of the Outworld menace he joins Liu Kang in entering Shao Kahn's contest.
- Jax: His real name is Major Jackson Briggs, leader of a top US special forces unit. After receiving a distress signal from Lt. Sonya Blade, Jax embarks on a rescue mission. One that leads him into a ghastly world where he believes Sonya is still alive.
- Baraka: He led the attack against Liu Kang's Shaolin temples. Baraka belongs to a nomadic race of mutants living in the wastelands of the Outworld. His fighting skills gained the attention of Shao Kahn who recruited him into his army.
- Kitana: Her beauty hides her true role as a personal assassin for Shao Kahn. Seen talking to an earth-realm warrior, her motives have come under suspicion by her twin sister Mileena. But only Kitana knows her own true intentions.
- Mileena: Serving as an assassin along with her twin sister Kitana, Mileena's dazzling appearances conceal her hideous intentions. At Shao Kahn's request she is asked to watch for her twin's suspected dissension. She must put a stop to it at any costs.
- Smoke: (silver palette swap of Sub-Zero/Scorpion/Reptile)
- Noob Saibot: (black palette swap of Sub-Zero/Scorpion/Reptile)
- Jade: (green palette swap of Kitana and Mileena)
- Kintaro: A large four-armed Shokan, who after hearing of Goro's defeat at the hands of Liu Kang vowed to avenge his comrade and crush Liu Kang in the Tournament. He serves as the supreme commander of Outworld's armed forces and is only second to Shao Kahn himself.
- Shao Khan: Shortly after conquering the realm of Edenia he focused on Earthrealm through the Mortal Kombat Tournament. After Goro had defeated the Great Kung Lao, the ninth Mortal Kombat Tournament was held by Khan's sorcerer, Shang Tsung. Tsung had lost to Liu Kang, an earth warrior, but Khan gave him one more chance as Tsung came up with a plan to lure Earth's chosen warriors to Outworld for a second tournament. Shao Khan tricked Earth's warriors into coming and now prepares to fight them in Mortal Kombat so he can finally conquer Earthrealm.
Mortal Kombat 3 universe
After losing many battles to Liu Kang, Shao Kahn enacts a 10,000 year-old plan where he would have his Shadow Priests, led by Shang Tsung, revive his former Queen Sindel, who unexpectedly died at a young age. However, she wouldn't be revived in the Outworld; she would be resurrected in the Earth Realm. This would allow Shao Kahn to cross the boundary lines and reclaim his queen. When Sindel is reincarnated in Earth Realm, Shao Kahn reaches across the dimensions to reclaim her. As a consequence of his action, the Earth Realm becomes a part of the Outworld, killing billions instantly. Only a few are spared, as Raiden protects their souls. He tells them that Shao Kahn must be stopped, but he cannot interfere; due to his status, he has no power in Outworld, and Earth Realm is partially merged with Outworld. Shao Kahn has unleashed extermination squads to roam throughout the Earth Realm and kill any survivors. Also, Raiden's protection only extends to the soul, not to the body, so his chosen warriors have to fight the extermination squads and repel Shao Kahn.
- Liu Kang: After the Outworld invasion, Liu Kang finds himself the prime target of Kahn's extermination squads. He is the Shaolin Champion and has thwarted Kahn's schemes in the past. Of all the humans, Kang poses the greatest threat to Shao Kahn's rule.
- Kung Lao: Kung Lao's plan to reform the White Lotus Society comes to a halt when Shao Kahn's invasion takes the earth by storm. As a chosen warrior Kung Lao must use his greatest fighting skills to bring down Shao Kahn's reign of terror.
- Jax: In failing to convince his superiors of the coming Outworld invasion, Jax prepares to covertly for the future battle with Kahn's minions. He fits both arms with indestructible bionic implants. This is a war Jax is prepared to win.
- Sonya Blade: Sonya disappears in the first tournament, but is later rescued by Jax. After returning to Earth, she and Jax try to warn the U.S. government of the looming Outworld menace. Lacking proof, they watch helplessly as Shao Kahn begins his invasion.
- Kano: Kano was thought to have been killed in the first tournament. Instead, he is found alive in the outworld where he again escapes capture by Sonya. Before the actual Outworld invasion, Kano convinces Kahn to spare his soul. Kahn needs someone to teach his warriors how to use Earth's weapons... Kano is the man to do it.
- Sub-Zero (Unmasked): The ninja returns... unmasked. Betrayed by his own clan, the Lin Kuei, he broke sacred codes of honor by leaving his clan and is marked for death. But unlike the ninja of old, his pursuers comes as machines. He must not only defend himself against the Outworld menace, but he must also elude his soulless assassins.
- Shang Tsung: Tsung is Shao Kahn's lead sorcerer. He once fell out of favor with his emperor after failing to win the Earth Realm through tournament battle. But the ever scheming Shang Tsung is instrumental in Kahn's conquest of Earth. He has now been granted more power than ever.
- Stryker: When the Outworld portal opens over a large city in North America, panic and chaos rage out of control. Kurtis Stryker was the leader of the Riot Control Brigade when Shao Kahn began taking souls. He finds himself the lone survivor of a city once populated by millions.
- Nightwolf: Nightwolf works as a historian and preserver of his peoples culture. When Kahn's portal opens over North America, Nightwolf uses the magic of his Shaman to protect his tribes sacred land. This area becomes a vital threat to Kahn's occupation of Earth.
- Kabal: As a chosen warrior, his identity is a mystery to all. It is believed he is a survivor of a attack by Shao Kahn's extermination squads. As a result, he is viciously scarred, kept alive by artificial respirators and a rage for ending Shao Kahn's conquest.
- Sindel: Sindel once ruled the Outworld at Shao Kahn's side as queen. Now 10,000 years later after her untimely death, she is reborn on Earth with evil intentions. Sindel is the key to Kahn's occupation of Earth.
- Sheeva: Sheeva was hand picked by Shao Kahn to serve as Sindel's personal protector. She becomes suspicious of Shao Kahn's loyalty toward her race of Shokan when he places Motaro as the head of his extermination squads. On the Outworld, Motaro's race of Centurions is the natural enemy of the Shokan.
- Sektor: Sektor is actually the code name for unit LK-9T9. He was the first of three Prototype Cybernetic Ninjas built by the Lin Kuei. Sektor was once a human assassin trained by the Lin Kuei. He volunteered for automation because of his loyalty to the clan. Sektor survives the Outworld invasion: he has no soul to take.
- Cyrax: Cyrax is unit LK-4D4, the second of three prototype Cybernetic Ninjas built by the Lin Kuei. Like his counterparts, his last program is to find and terminate the rouge ninja Sub Zero. Without a soul, Cyrax goes undetected by Shoa Kahn and remains a possible threat against his occupation of Earth.
- Smoke (Human): (blue palette swap of Sektor and Cyrax) Smoke, unit LK-7T2, is the third prototype cyber-ninja built by the Lin Kuei. He tried to escape the automation process with Sub-Zero but was captured. His memories were stripped away, leaving behind an emotionless killer. However, Sub-Zero believes that within this machine is a human soul trying to escape.
- Noob Saibot: (black palette swap of Kano)
- Motaro: In the realm of the Outworld, Motaro's race of Centaurians has long since come into conflict with the Shokan. When Shao Kahn formed special extermination squads to eliminate the chosen warriors of Earth, Motaro was appointed to headthis elite group of savage warriors.
- Shao Khan: Long ago, Shao Kahn rose to power in the Outworld, usurping the realm from Kitana's parents and taking Queen Sindel for his bride. Then she died. Now, centuries later, Sindel is reborn. And since Shang Tsung failed to win the Earth Realm through Mortal Kombat I and II, her rebirth is the means by which Kahn will finally seize the planet forever unless...
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Characters that became playable in later titles:
- Goro: boss in MK1, playable in MKT
- Kintaro: boss in MKT
- Jade: unlockable opponent in MK2, playable in Ultimate MK3
- Noob Saibot: unlockable opponent in MK2 and MK3, alter-ego of Sub-Zero
New characters introduced in later titles:
|U||Unlockable player character|
|-||Character not included|
|Playable since Mortal Kombat 1|
|Playable since Mortal Kombat 2|
|Playable since Mortal Kombat 3|
|Playable since Ultimate Mortal Kombat 3|
|Playable in Mortal Kombat Trilogy|
- Palette swaps
- Blue: Sub-Zero
- Yellow: Scorpion
- Green: Reptile
- Black: Noob Saibot
- Gray: Smoke (human)
- Red: Ermac
- Purple: Rain
- Variable: Chameleon
Kunoichis (female ninjas):
- Blue: Kitana
- Purple: Mileena
- Green: Jade
- Gray: Khameleon
- Red: Sektor
- Yellow: Cyrax
- Blue: Smoke (cyborg)