V'Ger is the main antagonist in Star Trek: The Motion Picture.
V'Ger was one of, if not the most powerful alien entity ever encountered by the Federation. The entity itself was the size of the island of Maui on Earth, while it generated a cloud measuring in at a staggering 82 AUs, making it large enough to envelope the entire solar system.
V'Ger was first identified in deep Klingon space, hidden in a massive cloud of energy, moving through the stars towards its final destination: Earth.
The cloud easily destroyed three of the Klingons' new K't'inga-class warships and the Federation monitoring station en route. Later on in the film, the newly refitted starship Enterprise intercepts the energy cloud. After getting the cloud to break off its attack on the Enterprise, Admiral Kirk orders the vessel to penetrate the cloud and discovers the massive vessel residing within. They then reach the front of the vessel and V'Ger then suddenly attacks the Enterprise. A probe appears on the bridge, attacks Spock and abducts the navigator, Ilia. V'Ger then uses its powerful tractor beam to move the Enterprise into its interior. Ilia suddenly reappears on the ship, now replaced by a robotic doppelganger, a probe sent by "V'Ger" to study the crew. Later, Spock takes an unauthorized spacewalk into V'Ger's core. He then minds melds with a massive model of Ilia in the center. Overloaded by information, Spock is knocked out. Later, after being rescued by Kirk, Spock reveals that V'Ger itself, is a living machine.
At the heart of the massive ship, V'Ger is revealed to be Voyager 6, a 20th-century Earth space probe believed lost. The damaged probe was found by an alien race of living machines that interpreted its programming as instructions to learn all that can be learned, and return that information to its creator. The machines upgraded the probe to fulfill its mission, and on its journey the probe gathered so much knowledge that it achieved consciousness.
Spock realizes that V'Ger lacks the ability to give itself a focus other than its original mission; having learned what it could on its journey home, it finds its existence empty and without purpose. Before transmitting all its information, V'Ger insists that the Creator come in person to finish the sequence. Realizing that the machine wants to merge with its creator, Decker offers himself to V'Ger, as he merges with the Ilia probe and V'Ger, creating a new form of life that disappeared from the physical realm.
A few weeks later, Spock had mental contact with Voyager while working to defuse a crisis on the Fabrini world ship Yonada. Afterwards Spock reported to Kirk that the part of Voyager that had been Decker seemed to be happy in his new life.
V'Ger is one of the few principal villains of the Star Trek movies to not be killed by the end of the movie. The others are the Whale Probe and Khan Noonien Singh (in the alternate reality).
V'Ger is memorable for being the first ever main antagonist in a Star Trek film.
For the 2001 Director's Edition of The Motion Picture, the size was scaled down from 82 AUs to 2 AUs. While this seems drastic, 1 AU is the distance from the Earth to the Sun, which still makes V'Ger one of the largest villains in Star Trek. In the novel Ex Machina the vessel itself is mentioned to be the size of Maui.