Ultroid Zero (ウルトロイドゼロ Urutoroido Zero) is an Ultraman-like robot manufactured by GAFJ as the fourth SAA Unit, incorporating the combat data of the Ultra Warriors they encountered up to that point (including Z) and King Joe STORAGE Custom.
Created during the disbandment of STORAGE, it was under the ownership of SAAG, STORAGE's successor. Instead of being designated to its combat preference, it was declared as "The Strongest Robot Weapon" (最強ロボット兵器 Saikyō Robotto Heiki).
As part of Celebro's final plan, Ultroid Zero later transforms into a Destrudos (デストルドス Desutorudosu) by fusing with the Kaiju Medals and other monsters around the world.