The MS-14J ReGelgu is the retrofitted version of MS-14A Gelgoog first deployed by the Axis Zeon during the First Neo Zeon War. The name ReGelgu stands for "Refined Gelgoog". The ReGelgu has several improvements over its predecessor, including an enhanced generator and built-in weapons. However, its true focus is on high mobility, possessing large shoulder binders, known as wing binders, which contain 10 thrusters and verniers to boost its maneuverability. It also has a pair of external propellant tanks on the backpack, extending its operating time. This backpack is also equipped with a missile pod and a pair of beam lancers. Other weapons include a grenade launcher and a beam rifle.
During the First Neo Zeon War, the Axis Zeon renamed themselves as Neo Zeon and fielded many advanced mobile suits, but their resources were limited compared to the Earth Federation and they needed to field any mobile suit available, even older machines such as the ReGelgu. One such unit was piloted by Neo Zeon Ace Illia Pazom. In U.C. 0096, a number of ReGelgus survived and would be used by the Neo Zeon remnants, the Sleeves, during the Laplace Incident. The Sleeves' ReGelgus would be repainted into a new color scheme and given the distinctive markings featured on many of the Sleeves' mobile suits. One such unit was destroyed by the Mega Bazooka Launcher operated by ECOAS field commander Conroy Haagensen.