Transformers are fictional alien robots and the titular characters of a popular Hasbro toy line and its spin-offs. They come from the planet Cybertron and are divided into the heroic Autobots, led by Optimus Prime, and the evil Decepticons, led by Megatron. They are able to "transform", rearranging their bodies into common or innocuous forms, including vehicles, devices or animals. Beyond that, they can displace mass (i.e. shrink and expand), combine with one another, and apply synthetic flesh (see: Transformers technology). This ability to transform is reflected in the programs' taglines "More Than Meets the Eye" and "Robots in Disguise". All Transformers stories and characters, in a range of media, have been based around this core concept since their debut in 1984.

The largest Transformers story arc, retroactively known as Transformers: Generation 1, includes both the TV series and Marvel comic, which further divided into Japanese and UK spin-offs respectively. Sequels followed, such as the Generation 2 comic book and Beast Wars TV series which became its own mini-universe. Generation 1 characters underwent two reboots with Dreamwave in 2002 and IDW Publishing in 2006. There have been other incarnations of the story based on different toy lines during the 2000s. The first was the Robots in Disguise series, followed by Armada/Energon and Cybertron. A live-action film was also released in 2007, again distinct from previous incarnations.