The Terminator, also known as a Cyberdyne Systems Model 101 or T-800, is the name of several film characters from the Terminator franchise portrayed by Arnold Schwarzenegger. The Terminator itself is part of a series of machines created by Skynet, an artificial intelligence, for infiltration-based surveillance and assassination missions. While an android for its appearance, it is usually described as a cyborg consisting of living tissue over a robotic endoskeleton.

The first appearance of the Terminator was as the eponymous main antagonist in The Terminator, a 1984 film directed and co-written by James Cameron. While the original Terminator was destroyed, other machines with the same appearance are featured in the sequels. In Terminator 2: Judgment Day (1991) and Terminator 3: Rise of the Machines (2003), Schwarzenegger's Terminator serves as the main protagonist, while in Terminator Genisys (2015) and Terminator: Dark Fate (2019), it serves as a supporting protagonist, and is pitted against other Terminators sent by Skynet and its successor Legion.

In Terminator Salvation (2009) and Dark Fate, the character also appears briefly as an antagonist. In the context of the stories, the plot device of having various robots looking the same provides a certain continuity for the human characters by exploiting their emotional familiarity with a particular "human" visage associated with each "model". The "Terminator" title is also used as a generic name for other human-simulating characters in the Terminator franchise, such as the liquid-metal T-1000 antagonist in Judgment Day.

The Terminator is Schwarzenegger's best-known role, and resulted in two catchphrases, "I'll be back" and "Hasta la vista, baby", used in the first and second film respectively.

A Terminator is an infiltration-based assassin, described in the films as a cybernetic organism. They are built in the future by Skynet, an artificial intelligence engaged in a war against humans. Often known as a T-800, the T-800 series is preceded by an earlier model known as the T-600 series, which used artificial rubber skin and was easily spotted by members of the human resistance.

T-800 models are all identical in appearance: a muscular, male human exterior made up of living tissue, covering a metal endoskeleton actuated by a powerful network of hydraulic servomechanisms, which provide superhuman strength. In the Terminator sequels, armies of skinless T-800 endoskeletons are shown to be used by Skynet during future war sequences, serving as soldiers rather than infiltrators. With the exterior appearance applied, they are the first Terminator model capable of blending in with humans; as a result, the resistance began using dogs to detect them, since the animals became agitated and barked loudly in their presence.

In the first film, a Terminator time travels from 2029 to 1984 to alter the past by killing Sarah Connor, retroactively ensuring victory for Skynet. Kyle Reese, a future soldier sent back to stop the Terminator, describes the latter as such:

The skin is prone to aging and injury related deterioration, but can heal itself with enough time. According to early drafts for the original film, a Terminator must consume small amounts of food to maintain the human skin, a detail that is absent in the finished film.