A former green beret and field operative for FOX, Naked Snake is the lone soldier sent into the Soviet Union. Following the defection of The Boss, his mentor, Snake must embark on a mission for the US government to assassinate the woman who taught him everything, uncovering many dark secrets about his country and others on the way. In actuality, Naked Snake is Big Boss, genetic father of Solid Snake.
Real name David Oh, Major Zero is Naked Snake's commanding officer. He formerly served in the British S.A.S (where he met The Boss) and with MI6, where he was codenamed "O", from which the codename "Zero" is derived. In 1962, Zero helped Sokolov and his family defect from the Soviet Union to America.
Para-Medic is a doctor, and serves as a medical advisor to Naked Snake during the Virtuous Mission and Operation Snake Eater. The failure of Operation Snake Eater would result in Para-Medic having her medical license revoked, and so assists Snake in any way she can (including sharing with him her endless love of movies, much to his dismay).
SIGINT provides details to Snake on weaponry, machinery, camouflage, and gadgetry. He, among other things, invented the binoculars Naked Snake uses during his mission. He also provides useful strategies and tactics in boss battles and other situations. His codename refers to the military term "SIGINT", or SIGnal INTelligence.
Born 1922, The Boss was Naked Snake's mentor. She taught him everything, and they together developed the combat technique of CQC, which Snake makes heavy use of in his missions. With her defection to the Soviet Union, she is determined to make Snake's mission to kill her and stop Colonel Volgin as hard as possible.
The Pain has the ability to control hornets at his will, which he obtained by letting hornets sting him countless times until they considered him one of their own. His codename comes from the pain he feels as a result of this (pain he has grown to love), and his desire to inflict equal pain on his opponent.
The Fear is known for his superhuman speed and agility; his elbows are double-jointed, and his tongue has been forked through surgery. Having a love for animals and the forest, he fights in trees, his preferred weapon being venom-coated darts which he fires from a crossbow. He also uses Stealth camouflage to turn invisible. His codename is derived from his gruesome appearance and frightening combat tactics, which he uses to inflict fear into his enemies.
The End is a legend, known as the father of modern sniping. At over 100 years old, The End is often asleep, claiming to be saving himself for one final battle - a battle he hopes to have with Naked Snake. The strange camouflage he wears gives him photosynthetic abilities (he can apparently call on the "spirits of the forest" for assistance and energy), and his pet parrot follows him everywhere, acting as his spotter. His codename is derived from his extreme age and the "true oblivion" he feels and represents.
A former Soviet Cosmonaut, The Fury is the Cobra unit's pyromaniac, armed with a flamethrower and seeing fire as the ultimate expression of his fury. Once, as he returned from space, his ship on fire caused him to see the world set ablaze, igniting a fury in him for the first time. It is this fury at the world and at "being alive" that gave him his codename.
The Sorrow was the former lover of The Boss. With The Boss' original name "The Joy", SIGINT jokes that there could not have been a more perfect pair. During a top secret mission, The Boss was forced to kill The Sorrow, but his spirit lives on. When alive, he served as the Cobra unit's "spirit medium soldier" and uses his psychic abilities to aid soldiers on the battlefield.
Colonel Volgin is the leader of a Soviet extremist faction - the group joined by The Boss after her defection. After inheriting the Philosophers' Legacy from his father, Volgin used the funds to create the Shagohod, a weapon of mass destruction that Snake must destroy if he is to accomplish his mission. Of course, Volgin himself must also be stopped.
Sokolov is the head developer of the Shagohod project, albeit unwillingly. He was captured by Volgin and forced to work for him, and although he originally escaped (with the help of Major Zero) several years earlier, he was returned to the Soviet Union as a result of the deal made during the Cuban Missile Crisis. It is Snake's mission in the Virtuous Mission and Operation Snake Eater to rescue him.
A GRU Major who leads a special unit within Spetsnaz, Ocelot is supposedly the son of a legendary soldier. He reports to Colonel Volgin, though his true ties are not entirely certain. After encountering Naked Snake during the Virtuous Mission, he gains an underlying respect for the CIA agent, certainly taking his advice about his choice of weapon to heart.
Granin is the director of OKB-812, the Granin Design Bureau. He originally imagined the concept a bipedal tank, although his designs were discarded in favour of Sokolov's.
An acquaintance of the Colonel, Raikov bears slightly more than a passing resemblance to a certain white-haired agent. As a major Raikov works in Groznyj Grad, watching over the guards there, although his Colonel-class authorisation is a result of "special treatment" by Colonel Volgin.