A living will—also known as an Advance Health Care Directive—is a document in which the declarant or principal (person making the living will) specifies what kind of medical treatment the declarant does and does not want if the declarant has a medical emergency and is unable to communicate those wishes. A living will may direct health care providers to administer, withhold, or withdraw life-sustaining treatments if the declarant is in a terminal or irreversible condition.

Laws and terminology for documents related to living wills, Advance Health Care Directives, Do Not Resuscitate orders (DNRs), and other health care documents vary from state to state. These laws are generally located in a state’s statutes—often in the probate code or estates code.

In New York, a living will is not specifically established by statute, but it is recognized by the courts as a valid expression of a person's wishes regarding medical treatment when they are unable to communicate due to incapacity. A living will typically outlines the types of life-sustaining treatment an individual does or does not want in the event they are in a terminal condition or permanently unconscious. This can include instructions on resuscitation, mechanical ventilation, artificial nutrition and hydration, and other end-of-life treatments. New York also recognizes Health Care Proxies, which allow individuals to appoint an agent to make health care decisions on their behalf if they are unable to do so. The combination of a living will and a Health Care Proxy provides a comprehensive approach to advance health care directives in New York. It is advisable for individuals to consult with an attorney to ensure that their living will and any other advance directives are properly drafted and reflect their wishes in accordance with New York law.