Mega Man X is the main protagonist of the Mega Man X series. He is the successor of the original Mega Man and is Dr. Thomas Light's greatest creation. Throughout the series, X is a Maverick Hunter who fights alongside his partners Zero and Axl in order to maintain peace and stability in the world and protect humans and Reploids alike from Maverick Reploids, though X would like nothing better than the opportunity to stop fighting. Because of his aversion to violence, X is initially ranked a B-Class Hunter, but he is eventually promoted to S-Class.
X is the first robot to possess sophisticated technology and behavioral adaptation, based on the last design of Dr. Light. Dr. Cain, the scientist who found him, was never able to fully analyze X's internal systems and system code. Despite this, Cain was able to replicate X's general architecture, making X the precursor to each and every Reploid brought into production. This makes him the proverbial 'father' of the Reploids. Though X and Zero are technically not Reploids, as they are the first of their kind, they are known as reploids to reduce confusion.
X's creation by the hands of Thomas Light during the later days of the original Mega Man series, but no exact dates were given. He was created with a unique system that allowed him to think, feel and act completely on his own. However, fearing that he would be a threat to the world because of the immaturity of his inexperienced circuits (or because the world wasn't ready for him according to Maverick Hunter X), Light sealed him away in a capsule that would test the reliability of his circuits to prove his maturity. Unfortunately, the system tests would take aproximately 30 years to complete, and Light knew he was going to pass away before then. With this in mind, he recorded a warning addressed to any future benefactors to not open the capsule until the tests were completed. On September 18th 20XX, Megaman X was sealed away.
X eventually passed all tests the capsule had prepared for him and he was found in the year 2114 by scientist Dr. Cain. Cain, not being an expert in robotics, was baffled by the design specifications Light had included on the computer as even a century later they were ahead of anything the world had ever seen. From these specifications and with the help of X, Cain began developing his own version of next-generation robots, which came to be known as Reploids. However, the Reploids never recieved the same testing as X. Apparently because of this oversight, over time more and more Reploids began to act strange and, eventually, become violent against humans and even other Reploids. These Reploids were deemed "Maverick" and, as incidents of Reploids going Maverick increased, the human government decided to find a department which was supposed to deal with the Maverick Hunters. Feeling responsible for this situation, X joined the Maverick Hunters and became part of Sigma's 17th Elite Unit.