The GAT-X103 Buster Gundam is a prototype artillery mobile suit introduced in the anime series Mobile Suit Gundam SEED. It was piloted by Dearka Elsman.

One of the five mobile suits developed as part of the Earth Alliance's G Project, the Buster Gundam is an artillery mobile suit and adopts the X100-series frame, similar to the one used by the GAT-X102 Duel Gundam. It has firepower rivaling that of a battleship and is meant to provide rear support for the other units and to attack enemy ships or facilities from a distance. Due to its role, the main sensor camera on Buster's head is very important and is protected with additional armor.

Its primary armaments are the gun launcher and high-energy rifle, both are energy intensive and have their own sub-generators. They can also combine to form the more powerful anti-armor shotgun or the hyper-impulse long-range sniper rifle, with the improved firepower seemingly caused by the linkage of the sub-generators. Although the suit has no close combat weapon, it has a pair of shoulder-mounted missile pods that can be used to discourage enemy units from closing in. Like other units in the G Project, Buster has Phase Shift armor, making it nearly impervious to physical weapons.