In the anime series Gundam Seed, ZAFT created a series of advanced mobile suits based on technology reverse-engineered from the captured Earth Alliance G Project suits. Like their EA predecessors, the ZAFT Gundams were armed with advanced beam weaponry and protected by Phase Shift armor. However, a additional technology was incorporated as well: the Neutron Jammer Canceller, which countered the effects of the ubiquitous N-Jammers and allowed these suits to be powered by nuclear reactors. This gave them almost limitless combat endurance, even with Phase Shift armor activated.

The first of these suits was the YMF-X000A Dreadnought Gundam, which appeared only in the manga side story Gundam SEED Astray. The Dreadnought Gundam was separate from the main ZGMF-X series, and served as a testbed for the N-Jammer Canceller and the DRAGOON (Disconnected Rapid Armament Group Overlook Operation Network) system of the ZGMF-X13A Providence Gundam. Unlike the other nuclear-powered Gundams, which were entirely new suits, the Dreadnought Gundam was actually built from a heavily modified ZGMF-600 GuAIZ frame. It was equipped with the ubiquitous beam rifle and CIWS guns, and a combined shield/beam saber, but the primary armament was a pair of "Pristis" beam reamers (beam cannon/scissor anchors) mounted on the hips. While these weapons were tethered to the suit by wires, they were completely DRAGOON controlled; the wires were simply to recover the weapons in the event of a malfunction in the still-experimental system.

The Dreadnought Gundam was test piloted by Courtney Heironimus, then acquired by the Junk Guild, and piloted by Prayer Reverie, a Newtype clone whose exact origins are unknown. Shortly before the war's end, it was upgraded by Lowe Gear with a new backpack mounting four large DRAGOON weapon pods, similar to those of the Providence Gundam. The configuration of the backpack caused Lowe to nickname the Dreadnought Gundam "X Astray". The final use of the Dreadnought Gundam was against Prayer's rival Canard Pars and his CAT1-X1/3 Hyperion Gundam Unit 1. In the end, the Hyperion Gundam was destroyed, but Prayer protected Canard from the explosion and died shortly thereafter due to flaws in the cloning process.

The Dreadnought Gundam was then rebuilt by Lowe as the YMF-X000A/H Dreadnought H (the "H" standing for "Hyperion", as elements of the Hyperion Gundam were incorporated into the design), and piloted by Canard. The DRAGOON system was removed, and its backpack was replaced with a pair of weapon pods, each mounting a combined beam cannon/long beam sword, an "Igelstellung II" vulcan, and a grenade launcher. In combat, the Dreadnought H could assume Buster Mode, in which the pods mounted over the shoulders for use as beam cannons, and Sword Mode, in which they mounted under the arms as beam swords. In Sword Mode, the vulcans and grenade launchers could also fire over the shoulders. In addition, the "Pristis" beam reamers were converted into "Armure Lumiere" mono-phase lightwave shield generators, and mounted on the forearms when in use. The long beam rifle was replaced by the "Zastava Stigmate" beam submachinegun from Hyperion. However, unlike Hyperion's submachinegun, which was powered by the battery pack on the gun, it was connected by a cable to the suit's reactor.

YMF-X000A Dreadnought Gundam

Manufacturer: Zodiac Alliance of Freedom Treaty
Users: Junk Guild
Unit type: prototype attack use mobile suit
Head height: 18.21 meters
Weight: 67.50 metric tons (without DRAGOON pod backpack)
Special equipment: Phase Shift armor, Neutron Jammer Canceller, DRAGOON (Disconnected Rapid Armament Group Overlook Operation Network) system
Powerplant: Ultracompact nuclear fission reactor
Armament: MA-M22Y high-energy beam rifle x1, MA-MV04 composite armed shield system with beam saber x1, MMI-GAU2 "Picus" 76mm CIWS x4, XM1 "Pristis" beam reamer (beam cannon/scissor anchor) x2, large DRAGOON pod (9 beam gun nozzles) x4
Pilot: Courtney Hieronimous, Prayer Reverie

YMF-X000A/H Dreadnought H

Manufacturer: Junk Guild
Users: Junk Guild
Unit type: prototype attack use mobile suit
Head height: 18.21 meters
Weight: unknown
Special equipment: Phase Shift armor, Neutron Jammer Canceller, "Armure Lumiere" mono-phase lightwave shield system
Powerplant: Ultracompact nuclear fission reactor
Armament: MMI-GAU2 "Picus" 76mm CIWS x4, beam cannon/long beam sword x2, "Igelstellung II" 40mm multi-barrel CIWS x2, grenade launcher x2; "Zastava Stigmate" RFW-99 beam submachinegun with "Romteknica" RBW Type 7001 beam bayonette x1, powered by internal reactor
Pilot: Canard Pars