Katherine "Kate" Brewster is a fictional character from the 2003 film Terminator 3: Rise of the Machines. In the film, she is portrayed by American actress Claire Danes.

Kate Brewster worked as a veterinarian before her office was destroyed by the T-X, who was looking for her and John Connor. In the ensuing chaos, Kate is rescued by another Terminator (the T-850 played by Arnold Schwarzenegger). In a stolen Toyota Tundra pick-up, she meets John Connor, and he explains the situation, although at first she believes he is insane.

When her fiance is killed by the T-X and his form is assumed, Kate travels with John and the Terminator to warn her father about Skynet, which the military is planning to activate. During the trip, the Terminator reveals several pieces of information: that the destruction of Cyberdyne only postponed the creation of Skynet (and, by extension, Judgement Day), that John Connor and Kate Brewster will be husband and wife, and joint commanders of the Tech-Com resistance movement, at some time in the future, and that its own model, the T-850 Model 101, is considered 'obsolete' in favor of the newer, more advanced T-X.

Arriving too late to stop the T-X, who assumed Kate's form to infiltrate the Skynet design compound, they discover that had they stopped the T-X, it wouldn't have mattered -- Skynet had already been activated, and was already taking control of Earth's computer systems, public and private. Kate's father, who was fatally shot by the T-X, tells the two of a secret location in the mountains, known as 'Crystal Peak', that (they believe) holds the key to shutting Skynet down permanently.

Meanwhile, Skynet has taken control of hundreds of experimental military robot prototypes, and begins a slow, purposeful elimination of the human race. As the Terminator, Kate and John attempt to reach the 'Safe Zone', the T-X arrives, but they briefly delay it by activating a particle accelerator, which generates a huge magnetic field that not only traps the T-X's metal endoskeleton down, but also 'rips off' its liquid-metal 'skin'.

As Kate and John arrive at the Safe Zone (minus the Terminator, as the T-X had used nanobots to corrupt its programming), the T-X arrives for one final showdown -- but is ultimately stopped when the T-850 overcomes the nanobots and sets off in pursuit. Eventually, the T-850 effectively commits 'suicide' by jamming its one remaining (and badly malfunctioning) hydrogen power cell into the T-X's mouth before it detonates in a massive explosion.

Riding the elevator to the bottom level of the Safe Zone, they are initially perplexed when no sign of any SkyNet-related computing equipment is found -- only an archaic 1960s-era radio system and several ancient computers. Kate puts the pieces together and tells John that the T-850's mission was to help them survive Judgement Day, not stop it. Connor then realizes that the 'Safe Zone' was simply a fallout shelter for VIPs such as the President, should the world fall into a nuclear war.

As the old radios come alive, with news of SkyNet's growing assault on humanity (and frantic calls for help that will never come), Connor picks up the microphone numbly and responds to the one intelligible call, and when asked who's in charge at Crystal Peak, pauses for a devastated second, and then responds with two words:

'I am'.

As Connor drops the microphone, the radios resume their terrified chatter, and (over a montage of images) narrates that SkyNet couldn't have been shut down, even *if* Crystal Peak was the location of its 'system core' -- in fact, there was no core; SkyNet needed none, as it was literally 'everywhere': it was connected to college computer systems, military networks, and private computers of all shapes and sizes.

Eventually, some survivors showed up at Crystal Peak, including Bridgit Pepperson and Walt Gifford. Together they survive the nuclear apocalypse that establishes Skynet's dominance. In an alternate future timeline, Kate Brewster sends back the reprogrammed T-850 which killed her husband to the past, to save him and her in their youth. ::"You're John Connor's spouse and second-in-command." It is also mentioned in T3 that John Connor went to middle school with Kate before the arrivals of the two Terminators (the T-800 and T-1000). This contradicts John's age as given in the previous entry, Judgment Day. The third film also contains several similar errors, including Sarah's date of birth and death.