An advance healthcare directive, also known as living will, personal directive, advance directive, medical directive or advance decision, is a legal document in which a person specifies what actions should be taken for their health if they are no longer able to make decisions for themselves because of illness or incapacity. In the U.S. it has a legal status in itself, whereas in some countries it is legally persuasive without being a legal document.

A living will is one form of advance directive, leaving instructions for treatment. Another form is a specific type of power of attorney or health care proxy, in which the person authorizes someone (an agent) to make decisions on their behalf when they are incapacitated. People are often encouraged to complete both documents to provide comprehensive guidance regarding their care, although they may be combined into a single form. An example of combination documents includes the Five Wishes in the United States.

One alternative to a conventional healthcare proxy is the values history, a "two-part advance directive instrument that elicits patient values about terminal medical care and therapy-specific directives. The goal of this advance directive is to move away from a focus on specific treatments and medical procedures to a focus on patient values and personal goals. Studies suggest that values regarding financial and psychological burden are strong motivators in not wanting a broad array of end-of-life therapies. Another alternative to a conventional healthcare proxy is the medical directive a document that describes six case scenarios for advance medical decision-making. The scenarios are each associated with a roster of commonly considered medical procedures and interventions, allowing the individual to decide in advance which treatments are wanted or not wanted under the circumstances.