The Transformers are a race of robotic warriors native to the planet Cybertron (Seibertron), each capable of transforming from powerful robots into vehicles, weapons, and other items.
U.S. Animated, Japan
The Transformers were created by the Quintessons as slave workers and warriors, but ultimately rebelled in the First Cybertronian War.
Marvel U.S., Marvel U.K.
The Transformers were created by Primus as warriors against the future threat of Unicron.
Elsewhere, their specific origins have been left vague.