Ultraman Zero is the son of Ultraseven. He was trained under Ultraman Leo after he was banished from the Land of Light by his father for attempting to take the Plasma Spark for himself. His training ultimately led to his redemption in his battle with Belial.

Zero is one of the most popular Ultras in the Ultraman Series' history, appearing many times over a decade since his debut.

Ultraman Zero was originally going to be called by the initial draft name Ultraseven Ax by Masayuki Gotoh and would have resembled an all-red version of his current appearance, minus his Color Timer in earlier concept art. His Zero Sluggers were originally called the Double I Sluggers and he had several different powers from what his base form currently has, such as a flame-covered dash. The Sluggers could also fuse into a bow and arrow, which was later implemented into Ultimate Zero. However, this decision was canceled, he was renamed "Ultraman Zero" and his body was partially colored blue as well.