In the Terminator franchise, a Terminator is an autonomous cyborg, typically humanoid, conceived as a virtually indestructible soldier, infiltrator, and assassin. A variety of models appear throughout the franchise. Within the fictional storyline, Terminators are created in a post-apocalyptic future by a computer AI known as Skynet, after it has launched war on humans. The machines are created to aid Skynet in its quest, and most are designed as infiltrators with a human appearance. Several Terminators throughout the franchise are reprogrammed by the human resistance to instead serve as protectors.

James Cameron introduced the first Terminator character in the 1984 film The Terminator, featuring a single cyborg simply called the "Terminator" or "Cyberdyne Systems Model 101", portrayed by Arnold Schwarzenegger.

Terminators are cyborgs designed as skilled killing machines. In most franchise media, the machines are created in a post-apocalyptic future by a computer AI, Skynet, after it has launched a nuclear war against humans. According to the first two films, Terminators were created after the war started. The films Terminator 3: Rise of the Machines and Terminator Salvation feature an altered timeline affected by the destruction of Cyberdyne Systems in Terminator 2: Judgment Day. In this new timeline, Terminators were created by Cyber Research Systems, starting with the T-1. Subsequent films also feature their own alternate timelines.

Terminators typically consist of an exterior made of living human tissue, covering a metal endoskeleton. The skin is prone to aging and injury related deterioration. Terminators are generally used as infiltration units, their appearance allowing them to blend in with humans. Dogs are used by the human resistance to detect Terminators in disguise. Although designed to kill people, several of the machines are reprogrammed by the resistance to instead serve as protectors.

Common Terminator traits include super strength, shapeshifting, vocal impersonation, and red eyes. A Terminator's point of view is also rendered in this color.

The original film The Terminator (1984) introduces a Cyberdyne Systems Model 101, also known as a T-800 and commonly referred to as simply the "Terminator". The character is portrayed by Arnold Schwarzenegger, who would return to play various incarnations of the machine throughout the film series. Originally an antagonist, the T-800 is usually depicted as a protector in later appearances.

Subsequent films have introduced other Terminator models:

The films have also featured several humans who later become part machine: