The GAT-X105B/ST Star Build Strike Gundam is a Gunpla featured in Gundam Build Fighters, it is an upgraded version of the GAT-X105B/FP Build Strike Gundam Full Package. It's built by Sei Iori and primarily controlled by Reiji

The Star Build Strike Gundam is an overhauled version of the GAT-X105B/FP Build Strike Gundam Full Package. Sei Iori designed this unit to shock participants all over the world in the Gunpla World Tournament. This unit retains all of the original weaponry from the Full Package, with some of them being redesigned and having new features added. The suit also sports a new backpack—the Universe Booster—armed with two beam cannons and can act as an independent fighter when separated.

The Star Build Strike also has three unique Plavsky Particles-manipulating systems: the Absorb System, the Discharge System and the Radial General Purpose (RG) System. These systems are the final product of Sei thinking outside of the Gundam-lore. The Absorb System allows Star Build Strike to absorb enemy beam attacks through the suit's shield. The Discharge System's main purpose is to create a "Plavsky Power Gate" that then allows the use of the absorbed particles to enhance the suit's performance in a specific area. The RG system allows the Plavsky particles to permeate both the outside and inside of the suit, and as a result, the suit's performance is increased. In this form, the Star Build Strike can also perform its strongest attack, the "RG Build Knuckle".

As Sei utilized the knowledge he gained from building the Build Gundam Mk-II when constructing the Star Build Strike, the Gunpla ends up having an inner frame similar to the former's movable frame and this subsequently gave rise to the RG System.