The Terminator series is an American cyberpunk media franchise created by James Cameron and Gale Anne Hurd. The franchise encompasses a series of films, comics, novels, and additional media, concerning battles between Skynet's synthetic intelligent machine network and John Connor's Resistance forces with the rest of the human race. Skynet's most well-known products in its genocidal goals are the various terminator models, such as the T-800 (Model 101), who was portrayed by Arnold Schwarzenegger from the original Terminator film in 1984, and similar units he also portrayed in the later films. By 2010, the franchise has generated $3 billion in revenue.[1]

The central theme of the franchise is the battle for survival between the nearly-extinct human race and the world-spanning synthetic intelligence that is Skynet. Skynet is positioned in the first film as a U.S. strategic "Global Digital Defense Network" computer system by Cyberdyne Systems which becomes self-aware. Upon activation, it immediately perceives all humans as a "security threat", and formulates a plan to systematically wipe out humanity itself. The system initiates a nuclear first strike against Russia, thereby ensuring a devastating second strike and a nuclear holocaust which it anticipates will instantly wipe out much of humanity. Indeed, it does, with approximately 3 billion casualties, more than half of the total human population at the time, in the resulting nuclear war. In the post-apocalyptic aftermath, Skynet later builds up its own autonomous machine-based military capability which includes the Terminators used against individual human targets and therefore proceeds to wage a persistent total war against the surviving elements of humanity, some of whom have militarily organized themselves into a Resistance. At some point in this future, Skynet develops the ability of time travel, and both it and the Resistance seek to use this technology in order to win the war; either by altering or accelerating past events in Skynet's favour, or by preventing or forestalling the (present) apocalyptic timeline.

In the franchise, Judgment Day (a reference to the biblical Day of Judgment) is referred to as the date on which Skynet becomes self-aware, decides to exterminate mankind, and launches a nuclear attack on Russia to provoke a nuclear counter-strike against the United States. Due to time travel and the consequent ability to change the future, several differing dates are given for Judgment Day in different films in the franchise. In Terminator 2: Judgment Day, Sarah states that Judgment Day will occur on August 29, 1997. However, the attack on Cyberdyne Systems in the second film results in the creation of new parallel timelines: in the continuity of Terminator 3: Rise of the Machines and Terminator Salvation, Judgment Day was postponed to July 25, 2004; in the separate chronology of Terminator: The Sarah Connor Chronicles, the attack on Cyberdyne Systems delayed Judgment Day to April 21, 2011.

In Terminator Genisys, the fifth film in the franchise, Judgment Day was believed to have been postponed to an unspecified day in October 2017, attributed to altered events in both the future and the past. Sarah and Kyle time travel to 2017 and seemingly defeat Skynet but the system core, contained inside a subterranean blast shelter, secretly survives, thus further delaying Judgment Day.