The MS-05B Zaku I was a mobile suit introduced in Mobile Suit Gundam.

The MS-05B was the late production variant of the Zaku I and the first mobile suit assigned to combat units. An improvement over the MS-05A Zaku I Early Type, the B Type was visually identical to the A Type, but featured an improved cockpit design and better armor material. Like its predecessor, the MS-05B's power transmission pipes were all fixed and contained inside its armor. However, as the B Type saw wider deployment than the A Type, the flaws of this design quickly became apparent: since the power pipes took up most of its internal space, it was very difficult to improve its generator output or swap out parts. The structures of its limbs were also very complex due to the internalized power system. These problems would later be addressed by the MS-06 Zaku II series. Its weapons included a custom machine gun, a 280mm bazooka, and a spike shield. It could also be equipped with the standard weapons used by the MS-06 series, including the 120mm machine gun and the heat hawk.