Abstract: A variable displacement fuel tank for aircraft is provided. The variable displacement fuel tank may be disposed within an upper medial portion (12) of a fuselage (18) of an aircraft (10). In one embodiment, a variable displacement fuel tank (20) includes a fuel bladder (22) adapted to contain fuel and a plurality of panels (30, 34, and 36) coupled to the fuselage (18) and acting on the fuel bladder (22) to restrain and control the shape of the fuel bladder (22). The variable displacement fuel tank (20) also include a power drive system (26) that operates to move the plurality of panels (30, 34, and 36) through a continuum of positions between fully deployed and stowed in order to maintain substantially zero ullage within the fuel bladder (22).