The protagonist of Metal Gear Solid 3: Snake Eater uses the codename Naked Snake before becoming Big Boss.
Naked Snake is a CIA operative and member of the FOX unit sent into the Soviet Union during Operation Snake Eater. The mission takes place in 1964 and follows his attempt to recover scientist Nikolai Sokolov, stop Colonel Volgin, and confront his former mentor, The Boss.
The game serves as a prequel to the earlier Metal Gear titles, so Naked Snake’s identity explains the origin of one of the series’ most important figures. After the events of the game, he receives the title Big Boss.
Naked Snake is not the same character as Solid Snake, Liquid Snake, or Solidus Snake. Those characters are later products of the Les Enfants Terribles cloning project.