Zero (ゼロ) is one of the three main characters of the Mega Man X series, as well as the protagonist of the Mega Man Zero series. He also makes an appearance as Biometal Model Z in the Mega Man ZX series.
A high ranking Maverick Hunter in the X series, and a legendary freedom fighter in the Zero series, he's a die hard warrior who doesn't hesitate to take action. However, behind his cold and emotionless attitude lies a wounded soul.
He was created by Dr. Albert W. Wily during the Mega Man series. As such, his designation is DWN-∞ (Infinity). He has the Maverick Virus contained in a gem inside his head which Sigma smashed the gem, causing the Maverick Virus to infect both Sigma and Zero. Subsequently, Zero no longer showed any signs of Maverick behavior while Sigma became a Maverick.