A device used in a hydraulic system to move fluid.

Most hand pumps are of the piston type, in which movement of the pump lever, or handle, moves a piston inside the pump.

Some hand pumps are single-acting, which means that they move fluid only during one stroke of the handle. No fluid is moved during the return stroke. Other hand pumps are double-acting, which means that they move fluid during both strokes of the handle.

Most aircraft hydraulic systems that use an engine-driven or electric motor-driven hydraulic pump have a hand pump as a backup in case the power pump fails.