Motor imagery is a mental process by which an individual rehearses or simulates a given action. It is widely used in sport training as mental practice of action, neurological rehabilitation, and has also been employed as a research paradigm in cognitive neuroscience and cognitive psychology to investigate the content and the structure of covert processes (i.e., unconscious) that precede the execution of action. In some medical, musical, and athletic contexts, when paired with physical rehearsal, mental rehearsal can be as effective as pure physical rehearsal (practice) of an action.

Motor imagery can be defined as a dynamic state during which an individual mentally simulates a physical action. This type of phenomenal experience implies that the subject feels themselves performing the action. It corresponds to the so-called internal imagery (or first person perspective) of sport psychologists.

Mental practice refers to use of visuo-motor imagery with the purpose of improving motor behavior. Visuo-motor imagery requires the use of one's imagination to simulate an action, without physical movement. It has come to the fore due to the relevance of imagery in enhancing sports and surgical performance.

Mental practice, when combined with physical practice, can be beneficial to beginners learning a sport, but even more helpful to professionals looking to enhance their skills. Physical practice generates the physical feedback necessary to improve, while mental practice creates a cognitive process physical practice cannot easily replicate.

When surgeons and other medical practitioners mentally rehearse procedures along with their physical practice, it produces the same results as physical rehearsal, but costs much less. But unlike its use in sports, to improve a skill, mental practice is used in medicine as a form of stress reduction before operations.

Mental practice is a technique used in music as well. Professional musicians may use mental practice when they are away from their instrument or unable to physically practice due to an injury. Studies show that a combination of physical and mental practice can provide improvement in mastering a piece equal to physical practice alone. This is because mental practice causes neuron growth that mirrors growth caused by physical practice. And there is precedent: Vladimir Horowitz and Arthur Rubinstein, among others, supplemented their physical practice with mental rehearsal.

Mental practice has been used to rehabilitate motor deficits in a variety of neurological disorders. Mental practice of action seems to improve balance in individuals with multiple sclerosis and in elderly women. For instance, mental practice has been used with success in combination with actual practice to rehabilitate motor deficits in a patient with sub-acute stroke. Several studies have also shown improvement in strength, function, and use of both upper and lower extremities in chronic stroke.

Some studies evaluated the effect of MI in gait rehabilitation after stroke however there was very low‐certainty evidence that motor imagery is more beneficial for improving gait (walking speed), motor function and functional mobility compared to other therapies, placebo or no intervention. Additionally, there was insufficient scientific evidence to assess the influence of MI on the dependence on personal assistance and walking endurance.