The ASW-G-XX Gundam Vidar is a mobile suit introduced in the second season of the anime Mobile Suit Gundam IRON-BLOODED ORPHANS. It is piloted by Gaelio Bauduin, who had adopted the alias 'Vidar'.

At an unknown point in time, the damaged ASW-G-66 Gundam Kimaris Trooper was brought to the Outer Lunar Orbit Joint Fleet (aka Arianrhod Fleet) and under the orders of Rustal Elion, it was overhauled into the Gundam Vidar for Vidar's use. During the overhaul, the damaged parts of the Gundam Frame were replaced with new parts produced using the current technology. As part of the overhaul process, the mobile suit first became the ASW-G-XK XK to test its systems, before it achieved its current final form. Overall, the suit spent a long time undergoing maintenance and adjustment, and only Rustal and a few others in the Arianhod Fleet were aware of its existence.

The cockpit structure of the Gundam Vidar has the characteristics of Gjallarhorn's mobile suits, and does not contain the connectors for the Alaya-Vijnana system. Instead, it is fitted with a pseudo Alaya-Vijnana system, the Alaya-Vijnana Type E, which has the same strength as the original but without the risk. Details of this system are only known by some of those in charge of the suit's development.

Another special feature is the third Ahab Reactor on the Gundam Vidar's back, in addition to the two in the Gundam Frame which already produces more than sufficient energy to power the mobile suit. This third reactor's true purpose is to grant the suit a new Ahab Wave frequency, hence concealing its true identity. Scanners simply report the Gundam Vidar as "Gjallarhorn Unit No. 21". The added weight of the third reactor does not affect the suit's mobility thanks to the excess output from the two Ahab reactors. To further conceal the suit's identity, its armaments discard those that would give the image of Kimaris, and center around light and fast weaponry.