In Star Trek: The Motion Picture, VGer is a fictional sentient life form based upon Voyager 6, a NASA probe.
It was discovered by sentient mechanical life forms, who found it, "repaired" it, assuming it was an artificial intelligence like themselves, and sent it back to Earth. While on the way back to Earth, VGer destroyed a Federation space station, and a Klingon fleet.
Admiral James T. Kirk, was assigned his old ship Enterprise, to go intercept VGer. When Kirk and crew finally makes contact with VGer, through the assimilation of Lt. Ilia, they find out what VGer really needs: To bond with the "Creator", Humans. Captain Willard Decker accepts the offer, and disappears with VGer to places unknown.
It has been speculated that there may be a connection between V'ger and The Borg, the Federation's biggest foe.