- Directors: Nelson Shin
- Producers: Joe Bacal, Tom Griffith, Nelson Shin, Margaret Loesch, Lee Gunther
- Writers: Ron Friedman
- Genres: Animation, Action, Adventure, Family, Sci-Fi
- Actors: Peter Cullen, Judd Nelson, Leonard Nimoy, Orson Welles, Robert Stack, Frank Welker
Unicron, a space-roaming artificial planet, destroys and eats robot planet Lithone, along with its population. A few of the inhabitants attempt to flee the planet in spaceships but only one gets away.
It is revealed that the evil Decepticons have gained control of the Transformers’ homeworld, Cybertron at some point in the intervening twenty years since the beginning of the struggle between the robotic warriors on Earth (The exact means by which this victory was attained was never revealed). The heroic Autobots are readying themselves on two of Cybertron’s moons for a strike against the Decepticons, preparing a supply shuttle for launch to Autobot City on Earth. Their transmission is intercepted by the Decepticons, who ambush the shuttle and kill its crew, consisting of Ironhide, Ratchet, Prowl, and Brawn. The Decepticons then attempt to use the ship to infiltrate Autobot City on Earth without being detected.
Meanwhile, on Earth, Daniel Witwicky and Hot Rod fish in a lake nearby Autobot City, discussing Daniel’s loneliness, as his father Spike is on one of the Autobot moon bases. They pick up the shuttle’s signature, and race up to Lookout Mountain to see it land, irritating the old Autobot Kup in the process. They notice its damaged exterior and spot Decepticons, upon which Hot Rod fires at the stowaways. After a brief battle pitting Hot Rod and Kup against the Decepticons Blitzwing and Shrapnel, the Decepticons begin their attack on Autobot City. The outnumbered Autobots, including Autobot City Commander Ultra Magnus, Blurr, Springer, Perceptor, and female Autobot Arcee, transform Autobot City into a battle fortress and both sides settle down for a long siege that lasts the rest of the day and all of the following night. Early in the battle, Ultra Magnus sends orders to alert Blaster to radio for assistance from their commander Optimus Prime. An attempt to thwart the transmission by Soundwave and his cassette Decepticons fails, and the next morning Optimus and the Dinobots arrive to successfully repel the Decepticon invaders, including the here far more competent Devastator, who is displayed as being far more effective and brutal when compared to his depictions in the Television series prior to the release of the film.
The movie was produced by Sunbow/Marvel simultaneous to G.I. Joe: The Movie. The writers of the G.I. Joe film asked for permission from Hasbro to kill a character, Duke. Hasbro not only approved the request but “insisted” that the writers of Transformers: The Movie adopt the same fate for Optimus Prime. However, Optimus Prime’s death sparked much controversy and incurred so much backlash that it caused the writers to make changes so that Duke simply ended up in a coma (and eventually woke up from the coma).