The GN-000 0 Gundam (pronounced Oh-Gundam) is the first GN Drive equipped mobile suit in the Mobile Suit Gundam 00 series. It was piloted by Ribbons Almark and later by Lasse Aeon.

The 0 Gundam was a general-purpose mobile suit developed during the Solar Power Wars, 15 – 20 years prior to the revelation of Celestial Being, and was completed around A.D. 2290. The first Gundam created by Celestial Being, it was also known as the first generation machine. Data obtained from it was used in creating the second generation Gundams such as the GNY-001 Gundam Astraea. Unbeknownst to the organization, the 0 Gundam's data was copied by Ribbons Almark and the Corner Family, who later used it to create the Throne series. Although Ribbons was once the 0 Gundam's pilot, he was not its official Gundam Meister as the suit did not switch its rollout color scheme (white, grey and yellow) to a custom one, a standard procedure whenever a Gundam has an official Meister.

While the completion of the GN Drive was an important step in the establishment of GN Drive-equipped mobile weapons, it also required the development of ancillary technologies and materials like E-Carbon that is capable of withstanding the machines' high output. No matter how revolutionary a specific part is, it would not be able to demonstrate its full capabilities until surrounding technologies have also developed enough. As such the completion of the 0 Gundam was a triumph as it established the basic concepts and systems for later Gundams. This included the use of the GN Drive as the main engine unit, use of the GN Drive's high output to drive beam weapons, presence of clavicle antennae on the torso for controlling GN Particles, and head-mounted v-fin antenna as well as twin eye camera.

Compared to later Gundams, the GN Drive's cone on the 0 Gundam's back was not only of a different design, it was also larger and protruded out more as the drive's ancillary/support systems were yet to be miniaturized. In terms of armaments, the suit has a Beam Saber, Beam Gun, and Gundam Shield for close to mid-range combat. During the Celestial Being's armed intervention in A.D. 2307-2308, the 0 Gundam was with the shadow support organization, Fereshte, who usually took out its GN Drive to power their Gundams. Fereshte eventually merged with the reborn Celestial Being, bringing the 0 Gundam along. The 0 Gundam's GN Drive was then removed and used in powering the GN-0000 00 Gundam, while the suit itself was stored in one of Celestial Being's resource satellites.

The 0 Gundam was later pulled out of storage for combat deployment during the final battle with the Innovators. Since there was no GN Drive left to power it, the 0 Gundam was fitted with a large GN Condenser, also known as particle storage tank, that gave it limited operational time. It also had a new color scheme of red, blue and yellow, and was renamed as 'GN-000 0 Gundam (Type A.C.D.)' (Actual Combat Deployment) to differentiate it from its original form. This version uses the same armament as the original's. Later in the battle, the 0 Gundam (Type A.C.D) was abandoned by the backup Gundam Meister Lasse Aeon after its particle reserves were depleted. It was then found by Ribbons, who reactivated the Gundam one last time using a GN Drive he had cut off from the 00 Gundam.