A G-suit is worn by aviators and astronauts subject to high accelerations to prevent loss of consciousness, commonly called blackout or G-LOC (G-induced Loss Of Consciousness). The G-suit has been developed in various shapes and sizes, but basically still uses compressed air to cause the suit to exert force on the lower body and legs during manoeuvres subject to high g-force loading. The pressure prevents the wearer's blood from being forced to lower extremities of the body, thus ensuring the brain is not deprived of blood, the cause of blackouts.

The first G-suit was developed by a team led by Wilbur R. Franks at the University of Toronto's Banting and Best Institute in 1941. The G-suits were made to be used by the Royal Air Force pilots during the war.

A new design of G-suit has been developed by the Germans, called Libelle G-suit. It is filled with liquid. As the pilot is subjected to the G-force, the liquid is pushed down to the pilot's leg by the same G-force. The result is a much faster response than the pneumatic version. Preliminary test shows that pilot wearing the Libelle G-suit can withstand a force of 10G with ease while the same pilot barely withstand 9G in regular G-suit. Libelle is the German word for dragonfly, which was where the idea come from.