Air Motor is a type of motor which does mechanical work by expanding compressed air. Air motors generally convert the compressed air to mechanical work through either linear or rotary motion. Linear motion can come from either a diaphragm or piston actuator, while rotary motion is supplied by either a vane type air motor or piston air motor.

Air motors have existed in many forms over the past two centuries, ranging in size from hand held turbines to engines of up to several hundred horsepower. Some types rely on pistons and cylinders, others use turbines. Many compressed air engines improve their performance by heating the incoming air, or the engine itself. Air motors have found widespread success in the hand-held tool industry and continual attempts are being made to expand their use to the transportation industry. However, air motors must overcome inefficiencies before being seen as a viable option in the transportation industry.

A widespread application of small air motors is in hand-held tools, power ratchet wrenches, drills, sanders, grinders, cutters, and so on. Though overall energy efficiency of pneumatics tools is low and they require access to a compressed-air source, there are several advantages over electric tools. They offer greater power density (a smaller pneumatic motor can provide the same amount of power as a larger electric motor), do not require an axillary speed controller (adding to its compactness), generate less heat, and can be used in more volatile atmospheres as they do not require electric power.