Liquid Snake is a fictional character from the Metal Gear franchise. Along with protagonist Solid Snake, he is a product of Les Enfants Terribles, a top-secret government project to artificially create soldiers by cloning the legendary soldier Big Boss. He first appears as the main antagonist in the original Metal Gear Solid, where he leads the rogue FOXHOUND unit in a hostile takeover of a nuclear disposal facility in Alaska. The character returns in Metal Gear Solid V: The Phantom Pain as a child mercenary nicknamed the White Mamba with his real name revealed to be Eli.

Liquid Snake (Japanese: リキッド・スネーク, Hepburn: Rikiddo Sunēku) was raised in the United Kingdom following his birth, and served as an operative for the British SAS and later became the field commander of FOXHOUND during Metal Gear Solid, leading Revolver Ocelot, Psycho Mantis, Sniper Wolf, Vulcan Raven, Decoy Octopus and the Genome Soldiers. He leads the hostile takeover of Shadow Moses Island, Alaska to acquire Big Boss's remains and use his genetic information to treat the mutations affecting his subordinates, the Genome Army. Liquid harbors a strong resentment towards Solid Snake, as he mistakenly believes that Snake received Big Boss's superior genes while he was given only the flawed genes. In reality, it is Liquid who carries superior genes.

Snake first meets Liquid after he is taken captive by the enemy and imprisoned in a medical room. The two battle each other multiple times throughout the story. First, Liquid tries to kill Snake by piloting a Hind D and pursuing him across the Communication Towers but Snake destroys the helicopter with anti-air Stinger missiles. Afterward, Liquid manipulates Snake into activating Metal Gear REX by disguising himself as Master Miller. Snake destroys REX but falls unconscious in the aftermath which allowed Liquid to take his brother to the top of REX's ruins and challenge to a fistfight. Snake prevails but Liquid survives again and pursues Snake in a jeep chase that results in a crash outside the island's facility. Just as he approaches Snake, Liquid suddenly succumbs to the same FOXDIE virus that had also been injected into Snake. Liquid's death leaves Snake in doubt of his own survival, as FOXDIE targets victims based on specific DNA.

Liquid's presence still had an influence. His right arm was transplanted posthumously as a replacement to Revolver Ocelot. This resulted in Liquid's voice and mannerisms to be utilized by Ocelot whenever Solid Snake is nearby, such as when his host is confronted by Snake during the hijacking of Metal Gear RAY from the disguised tanker. The rest of Liquid's body was being kept by an unspecified agency until being stolen by Hal Emmerich to fake Snake's death. Liquid's personality took over Ocelot once again during the climax of Solidus Snake's takeover of the Big Shell with the intent of rebelling against The Patriots. Liquid was the one to send Arsenal Gear crashing into Manhattan.

Liquid's consciousness seemingly takes over his host's body as Liquid Ocelot. However, Liquid's personality is ultimately revealed to be an elaborate facade by Ocelot made possible through a process of self-hypnosis, in order to trick the Patriots' AIs. The rest of Liquid's remains were used as spare body parts for Big Boss's restoration.

Liquid Snake's next official appearance is in a prequel. The youth is a 12-year-old child soldier named Eli (イーライ, Īrai) who fled from his home in England after learning about his nature as a clone. He becomes an active mercenary in the Angola-Zaire border region in Central Africa where he sets up his own mercenary unit consisting entirely of children, nicknamed the White Mamba (ホワイトマンバ, Howaito Manba) or "Nyoka ya Mpembe" due to being the only white child soldier in the region.

Venom Snake first encounters Eli in Masa Village after it is taken over by Eli's group. After being subdued, he is taken into Mother Base where the Diamond Dogs staff try to re-educate him and integrate him into normal society along with the other child soldiers. However, Eli resists this treatment and rebels against the Mother Base staff, focusing his hostility on Venom Snake, whom he believes to be his biological father (unaware of Venom Snake's true identity as Big Boss's decoy).

When Eli sneaks into a chopper during Snake's deployment to OKB Zero in Kabul, he catches the attention of the young psychic known as the Third Child, who uses Eli's will to activate Sahelanthropus and attack Snake. After Sahelanthropus is neutralized and transferred to Mother Base, the Third Child infiltrates the place and befriends Eli, giving him a vial containing the English strain of Skull Face's vocal cord parasite. The two plot out an elaborate escape plan which involves helping other child soldiers escape and fixing Sahelanthropus with the assistance of its creator Dr. Emmerich. Ultimately, Eli succeeds in reactivating Sahelanthropus and hijacks the Metal Gear from Mother Base, escaping alongside the Third Child and the other child mercenaries.