Mobile Suits are humanoid weapon systems in the Gundam anime series. Mobile suits were the first in a class of what are known in the Gundam fandom as mobile weapons. Other mobile weapons are the Mobile Armor, the Mobile Pod, and the Mobile Doll.
In the Universal Century, the main reasons for the mobile suit is the AMBAC or Active Mass Balance Auto Control and the Minovsky particle. The original AMBAC prototype only had two large limbs, but by moving those limbs, it allowed for near-thrusterless manueverability in space by changing it's center of mass. This presents one of the revolutions in how space warfare is fought. The other revolution would come from a type of nuclear reactor designed by Dr. Minovsky. Not only could his nuclear reactor be shrunk down to the size of a quartet of refrigerators, but it also produced a unique particle called the Minovsky particle. This particle could block out certain types of radiation, including radar and radio signals. This would force modern combat back into the visual range. The first production mobile suit would be the MS-01.
The most famous of the mobile suits is the original Gundam model RX-78-2 piloted by Amuro Ray in the first series titles Mobile Suit Gundam.
The name 'mobile suit' is believed by some to be a reference to 'Mobile Infantry', in the Robert A. Heinlein book, Starship Troopers.