Mega Man X, commonly known as “X”, was a new type of robot with the ability to make his own decisions. Recognizing the potential danger of this model, Light sealed X away in a diagnostic capsule for over 30 years of testing. X’s capsule was uncovered by an archaeologist named Dr. Cain almost 100 years after X’s creation. Excited by the possibilities X presented, Cain disregarded the warnings Light had logged in the capsule and created a legion of new robots that replicated X’s free will; these robots were called “Reploids”
However, a virus that caused Reploids to turn against humans (later discovered to be originated by Dr. Wily, and implanted in Zero) began to spread. These Reploids were dubbed “Mavericks”, and a force called the Maverick Hunters was formed to combat them. The Maverick Hunters were led by Sigma until he, too, became a Maverick and declared war against the humans. X took it upon himself to join the Maverick Hunters under the new leader Zero, on a mission to save Earth from Sigma.