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 legal document under the state's common law. A living will, or Advance Health Care Directive, allows an individual to outline their preferences for medical treatment in the event that they become unable to communicate their wishes due to a serious health condition. This document can include instructions on the use of life-sustaining treatment, artificial hydration and nutrition, and other end-of-life care decisions. New York also recognizes Health Care Proxies, which are legal documents that allow individuals to appoint someone else (a health care agent) to make medical decisions on their behalf if they are unable to do so. The requirements for creating a valid living will or health care proxy in New York include being of sound mind and having the document witnessed by two individuals. It is important for individuals to discuss their wishes with their appointed health care agent, family, and physicians to ensure that their preferences are understood and followed.