A medical ventilator, also called a respirator, is a machine designed to mechanically move breathable air into and out of the lungs, to provide the mechanism of breathing for a patient who is physically unable to breathe, or breathing insufficiently.

They serve as life-support devices for patients who have trouble breathing on their own.

Ventilators are mostly used in intensive care medicine, home care, emergency medicine, and in anesthesia (as a component of an anesthesia machine).