A living will—also known as an advance directive—is a legal document that specifies the type of medical care that an individual does or does not want in the event they are unable to communicate their wishes.

In the case of an unconscious person who suffers from a terminal illness or a life-threatening injury, doctors and hospitals consult the living will to determine whether or not the patient wants life-sustaining treatment, such as assisted breathing or tube feeding. In the absence of a living will, decisions about medical care become the responsibility of the spouse, family members, or other third parties.