Terminator 2: Judgment Day (commonly abbreviated as T2) is a 1991 action/science fiction film. It was directed, co-produced, and co-written by James Cameron, and stars Arnold Schwarzenegger, Linda Hamilton, Edward Furlong and Robert Patrick. It is the first sequel to the 1984 film The Terminator, and picks up ten years after the events of the first film. It follows Sarah Connor, her 10-year-old son John, and a protector from the future (as in the first film), as they try to prevent Judgment Day, a day in the future when machines will start to exterminate the human race.

T2 was a significant box office and critical success. It had an impact on popular culture, and is considered by many to be hugely influential in the genres of action and science fiction. The film's visual effects include many breakthroughs in computer-generated special effects, marking the first use of natural human motion for a CG character and the first computer generated main character.

In 1994, ten years after Sarah Connor (Linda Hamilton) destroyed the original Terminator that was programmed to kill her, two men arrive in Los Angeles from the year 2029. The first is a Terminator (Arnold Schwarzenegger) identical to the one that Sarah first encountered, while the second is an unknown man (Robert Patrick).

John Connor (Edward Furlong) is now living with foster parents. He has grown up being told by his mother that he would someday lead the remnants of the human race to ultimate victory against the machines. Sarah’s experiences have significantly changed who she is, making her tougher and more vigilant, leading people to think she is insane and getting her locked up in a mental institution, Pescadero State Hospital.

Meanwhile, the Terminator and the unknown man eventually locate John Connor. Then, there is a twist: the unknown man is not a human protector, as the audience assumes based on the first film. The killing machine from the first film is now the protector, and the other man is another Terminator trying to kill John. When the good Terminator rescues John, he reveals what is happening. He is a Model 101, reprogrammed by the future John Connor to act as his protector. The other Terminator is a T-1000, programmed to kill him. It is made of mimetic polyalloy, essentially liquid metal, allowing it to emulate anyone or anything of equal size, except "complex machines" like "guns and explosives" because they "have chemicals, moving parts." It can, however, form "knives and stabbing weapons."

When John learns that the T-1000 will copy Sarah and then kill her, he and the Terminator go to rescue her. Initially, Sarah is terrified by it, but after seeing it fight off the T-1000, she accepts that they need its help. As they escape the city, the Terminator tells her about the future of Skynet, the sentient computer that will destroy humans. He tells her about its creator, Miles Bennett Dyson (Joe Morton), who designs a learning computer that suddenly becomes self-aware on August 4, 1997. It begins learning at a geometric rate, and on August 29, 1997, it launches nuclear missiles that destroy most of humanity.

Eventually, Sarah, John, and the Terminator arrive in the desert at Enrique Salceda’s camp, who has preserved an underground weapons cache in the event that the war actually happens. Sarah plans to take John and flee over the border into Mexico. While at the camp, she realizes that by killing Dyson, she can prevent Skynet from being invented, preventing the war with the machines. After she leaves, John and the Terminator figure out what she is going to do and take off after her. At Dyson's home, Sarah attempts to snipe him, but when she misses, she finds herself unable to kill him up close in front of his family. When John and the Terminator arrive, they inform Dyson of the consequences of his research. They convince him that they must destroy everything related to his chip design, including the CPU and arm from the previous Terminator.

Sarah, John, the Terminator, and Dyson break into the Cyberdyne building and retrieve the parts from the first Terminator. While preparing explosives to destroy everything else, security alerts the police who show up in force. When the SWAT team enters the building, they fatally shoot Dyson who stays behind to trigger the detonator.

They escape in a SWAT van, with the T-1000 in pursuit, first in a helicopter, then a liquid nitrogen truck. The truck crashes into a steel mill, causing the tank to rupture and liquid nitrogen to spill everywhere, freezing the T-1000. Even though the Terminator shatters him, the pieces thaw and reassemble. The T-1000 and Model 101 begin to fight hand to hand, with the T-1000 stabbing him through the power cell with a metal pole, deactivating him. The T-1000, disguised as Sarah, goes to hunt John. As John is confronted by two Sarahs, the Terminator, who had reactivated itself using an alternate power source, shoots the T-1000 with a grenade launcher, throwing it back into a pit of molten metal, terminating it.

After John throws the parts from the first Terminator into the molten metal, the Terminator tells him that he too must be destroyed to prevent his technology from being used to create Skynet. He tells Sarah that he cannot self-terminate, and she must lower him into the steel. As he goes down, he reaches up with a thumbs up, the last thing to go under. The movie ends with a dark highway at night, and Sarah's repetition of the phrase that Reese told her in the first film. "The future is not set."

Three versions of the film exist: the Theatrical cut, a "Special Edition" of the film for Laserdisc, VHS, and DVD and an "Extended Special Edition" available only as an Easter Egg on the Ultimate Edition DVD. The "Extended Special Edition" was titled the director's cut on the European HD DVD release.

The special edition has been the same from release to release, with all the scenes that Cameron reinserted intact. There are, however, two scenes that Cameron shot but chose not to reinsert into the film which have been included as an accessible extra on most "Special Edition" releases. The first scene shows the T-1000's tactile approach to acquiring information about the physical world, "scanning" John's room with its fingertips, and eventually finding a hidden shoebox containing pictures and tapes of Sarah, seen at the end of the first film. The second scene is an alternate ending set in 2027 with an aged Sarah Connor reflecting on how Judgment Day was averted. The addition of these scenes is the only difference between the "Special Edition" and the "Extended Special Edition". This version can be accessed by pressing 8,2,9,9,7 (based on August 29, 1997, the date of Judgment Day) on the main menu of the DVD. The easter egg is only functional on the Ultimate Edition DVD (no longer produced); however, these scenes can be accessed at a certain point in the film with the interactive mode on the Extreme DVD. In addition, the Extreme edition contains several easter eggs, which include access to the theatrical version of the movie, and a preview for the Ultimate Edition DVD.

Shooting began on October 9, 1990, and was completed on April 4, 1991. The film won four Academy Awards: (Best Sound, Best Make Up, Best Visual Effects, and Best Sound Editing). Most of the key Terminator effects were provided by Industrial Light and Magic for computer graphics and Stan Winston for practical effects. The external shots of Cyberdyne Systems Corporation were filmed on location at an office building in Fremont, California.

According to the "Extreme Edition" DVD special features, Linda Hamilton's twin sister Leslie was used in scenes that required two Sarahs. She is the mirror image of Sarah in the scene where they open up the Terminator's head, and in the scene where the T-1000 impersonates Sarah, she is whichever one is farthest from the camera, alternating between the real Sarah and the T-1000 based on camera position.

The sawed-off shotgun used by Schwarzenegger throughout the film was a modified Winchester Model 1901 10ga lever-action shotgun, modified especially for the film to allow it to be "flip-cocked" by the actor in several of the film's scenes.

The movie was made for approximately $100 million, and at the time was the most expensive movie ever made. It was a box-office success, earning $204.8 million in the United States alone, and was the highest grossing film of 1991, beating out Robin Hood: Prince of Thieves and Beauty and the Beast. The original Terminator grossed only $38 million in the U.S. in its theatrical run, making Terminator 2's 434% increase a record for a sequel.

Upon its release, the theatrical cut ran 137 minutes. On November 24, 1993, the Terminator 2: Judgment Day: Special Edition cut of the film was released to Laserdisc and VHS, containing 17 minutes of never-before-seen footage including scenes with Michael Biehn reprising his role as Kyle Reese in a dream sequence. The subsequent "Ultimate Edition" and "Extreme Edition" DVD releases also contain this version of the film.

The Montreal Film Journal calls it "one of the best crafted Hollywood action flicks". Screenwriting guru Syd Field lauds the plot of Terminator 2, saying, for example, "every scene sets up the next, like links in a chain of dramatic action." The film was placed #33 on Total Film's 2006 list of The Top 100 Films of All Time. The film has a score of 8.3 on the Internet Movie Database and is ranked 79 on the site's list of top 250 movies. The film has a 97% fresh rating on Rotten Tomatoes.

In 2003, The American Film Institute released its list of the 100 greatest screen heroes and villains of all time. The Terminator appeared as number 48 on the list of heroes for its appearance in T2, as well as number 22 on the list of villains for its appearance in the first Terminator. This is the only instance where the "same" character appears on both lists, though technically they are different characters based on the same model.