Megatron is a fictional character from the Transformers franchise, created by Hasbro, and based on a toy design by Takara. He is a sentient robotic lifeform from the planet Cybertron. He is also the Supreme leader of the villainous faction (primarily the Decepticons) and primary antagonist in most works of Transformers fiction. He has the ability to transform between his robot shape and various weapons or vehicles, depending on which "universe" he is seen in. Within the fiction, he is often said to have named himself after the legendary Megatronus Prime, and similarly inspired the name of a later villainous character.

Read more about Megatron:  Transformers: Generation 1, Transformers, Transformers Animated, Transformers: Timelines (Transtech), Transformers: Prime