In Metal Gear Solid V: The Phantom Pain, the protagonist uses the identity Venom Snake.
The game begins with the character awakening from a nine-year coma after the destruction of Mother Base. He initially appears to be Big Boss, the legendary soldier who led the Militaires Sans Frontières. The story gradually reveals that the player character is actually a medic who underwent extensive surgery and hypnotherapy to become a body double for Big Boss.
This revelation explains why the character resembles Big Boss and why other figures accept him as the returning commander. The identity gives the real Big Boss time to operate elsewhere while Venom Snake leads Diamond Dogs and pursues revenge against Skull Face.
Venom Snake is not the same person as Solid Snake or Liquid Snake, who are later clones of Big Boss. He is also distinct from Naked Snake, the name used by Big Boss during the events of Metal Gear Solid 3. The alias therefore reflects both the deception and the character’s transformation.